Led unit for display and display apparatus having the same

ABSTRACT

A light emitting device for a display includes first LED sub-unit, second LED, and third LED sub-units, an insulating layer substantially covering the first, second, and third LED sub-units, and electrode pads electrically connected to the first, second, and third LED sub-units, in which the first LED sub-unit is disposed on a partial region of the second LED sub-unit, the second LED sub-unit is disposed on a partial region of the third LED sub-unit, the insulating layer has openings for electrical connection between the electrode pads, a common electrode pad is connected to the first, second, and third LED sub-units through the openings in the insulating layer, first, second, and third electrode pads are connected to the first, second, and third LED sub-units, respectively, through at least one of the openings, and the first, second, and third LED sub-units are configured to be independently driven using the electrode pads.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from and the benefit of United StatesProvisional Patent Application No. 62/608,297, filed on Dec. 20, 2017,U.S. Provisional Patent Application No. 62/613,333, filed on Jan. 3,2018, U.S. Provisional Patent Application No. 62/614,900, filed on Jan.8, 2018, U.S. Provisional Patent Application No. 62/638,797, filed onMar. 5, 2018, U.S. Provisional Patent Application No. 62/683,553, filedon Jun. 11, 2018, and United States Provisional Patent Application No.62/683,564, filed on Jun. 11, 2018, the disclosures each of which ishereby incorporated by reference for all purposes as if fully set forthherein.

BACKGROUND Field

Exemplary implementations of the invention relate generally to a lightemitting stacked structure and a display device including the same, andmore specifically, to a micro light-emitting diode for a display and adisplay apparatus including the same.

Discussion of the Background

Recently, display devices using light emitting diodes (LEDs) have beendeveloped. A display device using LEDs may be generally formed byforming individually-grown red (R), green (G), and blue (B) LEDstructures on a final substrate.

However, in addition to satisfying the needs for high-resolution andfull-color in a display device, there are continuously increasing needsfor a display device with a high level of color purity and colorreproducibility that can be manufactured in a relatively simplemanufacturing method.

A light-emitting diode (LED) generally refers to an inorganic lightsource and has been used in a wide range of fields, such as displaydevices, lamps for vehicles, and general lighting. Since an LED hasadvantages such as longer lifespan, lower power consumption, and quickerthan an existing light source, it has been quickly replacing theexisting light source.

To date, conventional LEDs have been mainly used as backlight sources indisplay devices. However, recently, micro LEDs have been developed as anext-generation display that is capable of generating images directlyfrom light emitting diodes.

Display devices generally emit various colors using mixed colors ofblue, green, and red. Each of the pixels of a display device includesblue, green, and red sub-pixels. A color of a specific pixel isdetermined based on the colors of these sub-pixels, and an image isimplemented by a combination of these pixels.

In a micro LED display, micro LEDs are arranged on a two-dimensional(2D) plane to correspond to each sub-pixel, and thus, may require anarrangement of a large number of micro LEDs on a single substrate.However, a micro LED generally has a small form factor, such as asurface area of about 10,000 square micrometers or less, which may causevarious issues during manufacture due to its small form factor. Forexample, handling a micro LED is difficult due to the small form factor,and thus, it is difficult to mount the large number of micro LEDsrequired for a typical display panel, which can exceed millions of microLEDs.

Further, since the sub-pixels are arranged on a two-dimensional plane,an area occupied by one pixel that includes blue, green, and redsub-pixels is relatively large. As such, arranging sub-pixels within alimited area may require reducing the area of each LED chip, which inturn may deteriorate brightness of sub-pixels due to reduction of alight emitting area.

The above information disclosed in this Background section is only forunderstanding of the background of the inventive concepts, and,therefore, it may contain information that does not constitute priorart.

SUMMARY

Light emitting diodes constructed according to the principles and someexemplary implementations of the invention and displays using the samehave a stacked, light emitting structure that is simple and can be madein a simple manufacturing method. For example, the sides of the LEDstacks may have a predetermined inclination to facilitate forming anoptically non-transmissive film disposed on the sides of the LED stacksto prevent light leakage. Further, when each of the LED stacks has atapered shape at a predetermined angle, the light reflection effect ofthe optically non-transmissive film may be maximized or substantiallyincreased. As such, the angles between the sides of each of the LEDstacks and the one surface of the substrate may be the same or differentfrom each other.

Light emitting diodes and display using the light emitting diodes, e.g.,micro LEDs, constructed according to the principles and some exemplaryimplementations of the invention provide a light-emitting diode pixelfor a display which allow a plurality of pixels to be simultaneouslymanufactured so as to obviate the process of individually mounting theplurality of pixels.

Light emitting diodes and display using the light emitting diodes, e.g.,micro LEDs constructed according to the principles and some exemplaryimplementations of the invention provide a light emitting device for adisplay capable of increasing the luminous area of each sub-pixelwithout increasing the pixel area.

Light emitting diodes and display using the light emitting diodes, e.g.,micro LEDs constructed according to the principles and some exemplaryimplementations of the invention provide a light emitting device for adisplay capable of reducing the process time associated with mountingthe LEDs.

Light emitting diodes and display using the light emitting diodes, e.g.,micro LEDs constructed according to the principles and some exemplaryimplementations of the invention provide a light emitting diode for adisplay having a high reliability and a stable structure. For example,providing LED stacks and bonding layers with inclined side surfaces mayreduce or prevent the likelihood of disconnection of a connectorelectrically communicating with the LED stacks, as compared to when theLED stacks and the bonding layers have vertical side surfaces, and thus,reliability of the pixel may be enhanced. As another example, one ormore hydrophilic material layers may be used to improve the adhesion ofone or more bonding layer provided in or between the LED stacks, therebyreducing or preventing the occurrence of the peeling. As yet anotherexample, one of more shock absorbing layers may be used in the LEDstacks to reduce or prevent the occurrence of defects, such as peel-off.

Light emitting diodes and display using the light emitting diodes, e.g.,micro LEDs constructed according to the principles and some exemplaryimplementations of the invention are capable of being driven in one of apassive matrix driving manner and an active matrix driving manner.

Additional features of the inventive concepts will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the inventive concepts.

A light emitting stacked structure according to an exemplary embodimentincludes a substrate including an upper surface and a lower surface, aplurality of sequentially stacked epitaxial sub-units disposed on thesubstrate and configured to emit light of different wavelength bands,each epitaxial sub-unit has a light emitting region that overlaps withthe light emitting region of an adjacent epitaxial sub-unit, and asubstantially, non-transmissive film covering at least a portion of sidesurfaces of the epitaxial sub-units, in which the side surfaces of theepitaxial sub-units are inclined with respect to one of the upper andlower surfaces of the substrate.

An angle formed between the side surfaces of the epitaxial sub-units andthe upper surface of the substrate may be about 45 degrees to about 85degrees.

The epitaxial sub-units may include first, second, and thirdsequentially stacked epitaxial stacks.

A side surface of at least one of the first, second, and third epitaxialstacks may form an angle with one of the upper and lower surfaces of thesubstrate that is different from an angle formed by a side surface ofother one of the first, second, and third epitaxial stacks and the onesurface of the substrate.

The epitaxial sub-units may be disposed on the upper surface of thesubstrate, and light from the epitaxial sub-units may be configured tobe emitted in a direction away from the upper surface of the substrate.

Each of the epitaxial sub-units may have a peripheral region surroundingthe light emitting region, and the substantially, non-transmissive filmmay be disposed in the peripheral region.

The epitaxial sub-units may be disposed on the upper surface of thesubstrate, and light from the epitaxial sub-units may be configured tobe emitted in a direction toward the lower surface of the substrate.

The substantially, non-transmissive film may overlap the epitaxialsub-units in a plan view.

The substantially, non-transmissive film may include at least one of alight reflective film and a dielectric mirror.

The substantially, non-transmissive film may include metal.

The epitaxial sub-units may be configured to be driven independently ofeach other.

Light emitted from each of the epitaxial sub-units may have differentenergy bands, and light emitted from each of the epitaxial sub-units mayhave energy bands in an increasing order from the lowermost epitaxialsub-unit to the uppermost epitaxial sub-unit.

Light emitted from one of the epitaxial sub-units may be configured tobe transmitted through another epitaxial sub-unit disposed thereabove.

At least one of the epitaxial sub-units may be configured to transmitabout 80% or more of light emitted from the epitaxial sub-unit disposedthereunder.

The epitaxial sub-units may include a first epitaxial stack configuredto emit a first color light, a second epitaxial stack disposed on thefirst epitaxial stack and configured to emit a second color light havinga wavelength band different from the first color light, and a thirdepitaxial stack disposed on the second epitaxial stack and configured toemit a third color light having a wavelength band different from thefirst and second color light.

The first, second, and third color light may be red light, green light,and blue light, respectively.

The light emitting stacked structure may include a micro light emittingdiode having a surface area less than about 10,000 square μm.

The first color light may be any one of red, green, and blue light, thesecond color light may be any one of red, green, and blue lightdifferent from the first color light, and the third color light may beany one of red, green, and blue light different from the first andsecond color light.

At least one of the first, second, and third epitaxial stacks may haveirregularities formed on an upper surface thereof.

A display device including a plurality of pixels, in which at least someof which comprise the light emitting stacked structure according toexemplary embodiments.

The display device may be configured to be driven in one of a passivematrix manner and an active matrix manner.

A light-emitting diode (LED) pixel for a display according to anexemplary embodiment includes a first LED sub-unit, a second LEDsub-unit disposed on the first LED sub-unit, a third LED sub-unitdisposed on the second LED sub-unit, a connector disposed on at leastone side surface of the first, second, and third LED sub-units andelectrically connected to at least one of the LED sub-units, and aninsulating layer to insulate the connector from the at least one sidesurface of the LED sub-units, in which the at least one side surface ofthe LED sub-units is inclined with respect to a bottom surface of one ofthe first, second, and third LED sub-units, and the connector isdisposed on the inclined side surface of the LED sub-units.

The first LED sub-unit, the second LED sub-unit, and the LED sub-unitmay include a first LED stack, a second LED stack, and a third LEDstack, respectively, and the first, second, and third LED stacks may beconfigured to emit red light, green light and blue light, respectively.

The LED pixel may include a micro light emitting diode having a surfacearea less than about 10,000 square μm.

The first LED sub-unit may be configured to emit any one of red, green,and blue light, the second LED sub-unit may be configured to emit adifferent one of red, green, and blue light from the first LED sub-unit,and the third LED sub-unit is configured to emit a different one of red,green, and blue light from the first and second LED sub-units.

Light generated in the first LED sub-unit may be configured to passthrough the second and third LED sub-units and be emitted to the outsideof the LED pixel, light generated in the second LED sub-unit may beconfigured to pass through the third LED sub-unit and be emitted to theoutside of the LED pixel, the second LED sub-unit may be disposed on apartial region of the first LED sub-unit, and the third LED sub-unit maybe disposed on a partial region of the second LED sub-unit.

Light generated in the first LED sub-unit may be configured to beemitted to the outside of the LED pixel without passing through thesecond LED sub-unit, and light generated in the second LED sub-unit maybe configured to be emitted to the outside of the LED pixel withoutpassing through the third LED sub-unit.

The LED pixel may further include a substrate on which the first LEDsub-unit is disposed, in which the substrate includes GaAs, and thefirst LED sub-unit includes AlGaInP-based semiconductor layers.

The LED pixel may further include a distribution Bragg reflectorinterposed between the substrate and the first LED sub-unit, in whichthe distribution Bragg reflector includes semiconductor layers.

The LED pixel may further include through-vias passing through thesubstrate, in which the through-vias includes a first through-viaelectrically connected to a second conductivity type semiconductor layerof the first LED sub-unit, a second through-via electrically connectedto a second conductivity type semiconductor layer of the second LEDsub-unit, and a third through-via electrically connected to a secondconductivity type semiconductor layer of the third LED sub-unit, and theconnector is electrically connected to at least one of the first,second, and third through-vias.

The LED pixel may further include a first bonding layer interposedbetween the first and second LED sub-units, and a second bonding layerinterposed between the second and third LED sub-units, in which each ofthe first and second bonding layers includes an inclined side surface,and the connector is disposed on at least one of the inclined sidesurfaces of the first and second bonding layers.

The LED pixel may further include a first ohmic electrode interposedbetween the first and second bonding layers, the first ohmic electrodebeing in ohmic contact with the second LED sub-unit, and a second ohmicelectrode interposed between the second and third bonding layers, thesecond ohmic electrode being in ohmic contact with the third LEDsub-unit.

A first conductivity type semiconductor layer of the first LED sub-unit,a first conductivity type semiconductor layer of the second LEDsub-unit, and a first conductivity type semiconductor layer of the thirdLED sub-unit may be electrically connected to one another.

A display apparatus may include a circuit board, and a plurality ofpixels arranged on the circuit board, in which at least some of thepixels include the LED pixel according to exemplary embodiments.

The circuit board may include a passive circuit or an active circuit andthe first through third LED sub-units may be electrically connected tothe circuit board.

A light emitting device for a display according to an exemplaryembodiment includes a first LED sub-unit, a second LED sub-unit disposedbelow the first LED sub-unit, a third LED sub-unit disposed below thesecond LED sub-unit, an insulating layer substantially covering thefirst, second, and third LED sub-units, and electrode pads electricallyconnected to the first, second, and third LED sub-units, the electrodepads including a common electrode pad, a first electrode pad, a secondelectrode pad, and a third electrode pad, in which the first LEDsub-unit is disposed on a partial region of the second LED sub-unit, thesecond LED sub-unit is disposed on a partial region of the third LEDsub-unit, the insulating layer has openings for electrical connectionbetween the electrode pads, the common electrode pad is connected to thefirst, second, and third LED sub-units through the openings in theinsulating layer, the first, second, and third electrode pads areconnected to the first, second, and third LED sub-units, respectively,through at least one of the openings, and the first, second, and thirdLED sub-units are configured to be independently driven using theelectrode pads.

Light generated in the first LED sub-unit may be configured to beemitted to the outside of the light emitting device through the secondLED sub-unit and the third LED sub-unit, and light generated in thesecond LED sub-unit may be configured to be emitted to the outside ofthe light emitting device through the third LED sub-unit.

The first, second, and third LED sub-units may include first, second,and third LED stacks configured to emit red light, green light, and bluelight, respectively.

The light emitting device may include a micro light emitting diodehaving a surface area less than about 10,000 square μm.

The first LED sub-unit may be configured to emit any one of red, green,and blue light, the second LED sub-unit may be configured to emit adifferent one of red, green, and blue light from the first LED sub-unit,and a third LED sub-unit may be configured to emit a different one ofred, green, and blue light from the first and second LED sub-units.

The light emitting device may further include a first transparentelectrode interposed between the first LED sub-unit and the second LEDsub-unit and in ohmic contact with a lower surface of the first LEDsub-unit, a second transparent electrode interposed between the secondLED sub-unit and the third LED sub-unit and in ohmic contact with alower surface of the second LED sub-unit, and a third transparentelectrode disposed to be in ohmic contact with an upper surface of thethird LED sub-unit, in which at least some of the openings in theinsulating layer expose the first, second, and third transparentelectrodes.

One of the openings in the insulating layer may expose the secondtransparent electrode and the third transparent electrode together.

The first, second, and third LED sub-units may each include a firstconductivity type semiconductor layer and a second conductivity typesemiconductor layer, the first, second, and third transparent electrodesmay be electrically connected to the second conductivity typesemiconductor layers of the first, second, and third LED sub-units,respectively, and the second conductivity type semiconductor layer ofthe third LED sub-unit may be disposed on a partial region of the firstconductivity type semiconductor layer of the third LED sub-unit.

The first LED sub-unit and the second LED sub-unit may be disposed in anupper region of the second conductivity type semiconductor layer of thethird LED sub-unit.

The second and third electrode pads may be electrically connected to thefirst conductivity type semiconductor layer of the second LED sub-unitand the first conductivity type semiconductor layer of the third LEDsub-unit, respectively.

The second and third electrode pads may be directly connected to thefirst conductivity type semiconductor layers of the second LED sub-unitand the third LED sub-unit, respectively.

The light emitting device may further include a first color filterdisposed between the third transparent electrode and the secondtransparent electrode, and a second color filter disposed between thesecond LED sub-unit and the first transparent electrode.

The first color filter and the second color filter may includeinsulating layers having refractive indices different from each other.

The light emitting device may further include a first bonding layerinterposed to between the first color filter and the second transparentelectrode, and a second bonding layer interposed between the secondcolor filter and the first transparent electrode.

The light emitting device may further include a substrate connected to alower surface of the third LED sub-unit, in which the substrate includeat least one of a sapphire material and a gallium nitride material.

The second LED sub-unit and the third LED sub-unit may be connected incommon through one of the openings in the insulating layer.

The light emitting device may further include an ohmic electrodedisposed between the electrode pads and the first LED sub-unit and inohmic contact with the first LED sub-unit, in which the first electrodepad is connected to the ohmic electrode, and the insulating layercomprises at least one of a light reflecting layer and a light absorbinglayer.

A display apparatus may include a circuit board having a driving circuitto drive the light emitting devices in an active matrix driving mode orpassive matrix driving mode, and a plurality of light emitting devicesflip-bonded on the circuit board, in which at least some of the lightemitting devices include the light emitting device according toexemplary embodiments, in which the electrode pads are electricallyconnected to the circuit board.

The light emitting devices may include respective substrates adjoined tothe third LED sub-unit, and the substrates may be spaced apart from eachother.

A light emitting diode (LED) stack for a display according to anexemplary embodiment includes a first LED sub-unit including a firstconductivity type semiconductor layer and a second conductivity typesemiconductor layer, a second LED sub-unit disposed on the first LEDsub-unit, a third LED sub-unit disposed on the second LED sub-unit, afirst bonding layer disposed between the first and second LED sub-units,a second bonding layer disposed between the second LED and third LEDsub-units, and at least one buffer layer disposed between adjacent LEDsub-units.

The buffer layer may include a first hydrophilic layer contacting atleast two of the first LED sub-unit, the first bonding layer, the secondbonding layer, and the second LED sub-unit.

The LED stack may further include a support substrate disposed below thefirst LED sub-unit, a third bonding layer disposed between the supportsubstrate and the first LED sub-unit, and a second hydrophilic layerdisposed on a surface of the support substrate, in which the first andsecond hydrophilic layers may include at least one of a SiO2 layer and asurface modified layer.

The LED stack may further include an ohmic electrode in ohmic contactwith the first conductivity type semiconductor layer of the first LEDsub-unit, and disposed between the first LED sub-unit and the supportsubstrate, a reflective electrode in ohmic contact with the secondconductivity type semiconductor layer of the first LED sub-unit, anddisposed between the first LED sub-unit and the support substrate, aninterconnection line disposed below the first LED sub-unit, insulatedfrom the reflective electrode, and connected to the ohmic electrode, andan insulating layer insulating the interconnection line from thereflective electrode, in which the third bonding layer is in contactwith the interconnection line and the insulating layer.

Light generated in the first LED sub-unit may be configured to betransmitted through the second LED sub-unit and the third LED sub-unitand emitted to the outside of the LED stack, and light generated in thesecond LED sub-unit may be configured to be transmitted through thethird LED sub-unit and emitted to the outside of the LED sub-unit.

The first, second, and third LED sub-units may be configured to emit redlight, green light, and blue light, respectively.

The LED stack may include a micro light emitting diode having a surfacearea less than about 10,000 square μm.

The first LED sub-unit may be configured to emit any one of red, green,and blue light, the second LED sub-unit may be configured to emit adifferent one of red, green, and blue light from the first LED sub-unit,and the third LED sub-unit may be configured to emit a different one ofred, green, and blue light from the first and second LED sub-units

The LED stack may further include a first color filter interposedbetween the first bonding layer and the second LED sub-unit, andconfigured to transmit light generated in the first LED sub-unit andreflect light generated in the second LED sub-unit, and a second colorfilter interposed between the second bonding layer and the third LEDsub-unit, and configured to transmit light generated in the first andsecond LED sub-units, and reflect light generated in the third LEDsub-unit.

At least one of the first color filter and the second color filter mayinclude a SiO₂ layer, and at least one of the first bonding layer andthe second bonding layer may be in contact with the SiO₂ layer.

A display apparatus may include a plurality of pixels aligned on asupport substrate, in which at least some of the pixels may include theLED stack according to exemplary embodiments.

The second and third LED sub-units may each include a first conductivitytype semiconductor layer and a second conductivity type semiconductorlayer, the first conductivity type semiconductor layers of the first,second, and third LED sub-units of each pixel are electrically connectedto a common line, and the second conductivity type semiconductor layersof the first, second, and third LED sub-units are electrically connectedto different lines.

The common line may include a data line, and the different lines mayinclude scan lines.

The buffer layer may include a shock absorbing layer configured tocushion impact between the two adjacent LED sub-units.

At least one of the first and second bonding layers may be disposed onthe shock absorbing layer.

The shock absorbing layer may be disposed on at least one of the firstand second bonding layer.

At least one of the first and second bonding layers may include spin onglass (SOG).

The shock absorbing layer may include silicon oxide.

The buffer layer may include a first buffer layer disposed between thefirst and second LED sub-units, and a second buffer layer disposedbetween the second and third LED sub-units.

A thickness of the first buffer layer may be greater than a thickness ofthe second buffer layer.

Each of the first buffer layer and the second buffer layer may include ashock absorbing layer to cushion impact between the two adjacent LEDsub-units, and the shock absorbing layer of the first buffer layer mayhave a greater thickness than the shock absorbing layer of the secondbuffer layer.

The LED stack may further include a first wavelength pass filterdisposed between the first LED sub-unit and the first buffer layer, anda second wavelength pass filter disposed between the second LED sub-unitand the second buffer layer.

The LED stack may further include a contact disposed on the LEDsub-units to apply a common voltage and a light emitting signal, inwhich the contact may include first and second common contacts to applythe common voltage to the first, second, and third LED sub-units, andfirst, second, and third contacts to apply the light emitting signal toeach of the first, second, and third LED sub-units.

The LED stack may further include first, second, and third signal linesto apply the light emitting signal to the first, second, and third LEDsub-units, and a common line to apply the common voltage to the first,second, and third LED sub-units, in which the first, second, and thirdsignal lines may be connected to the first, second, and third contacts,respectively, and the common line may be connected to the first andsecond common contacts.

The first, second, and third signal lines may extend substantially in afirst direction, and the common line may extend substantially in asecond direction intersecting the first direction

The first common contact may be disposed under the first LED sub-unit.

A display device may include a plurality of pixels, at least some whichmay include the light emitting diode stack according to exemplaryembodiments.

The display device may be configured to be driven in one of a passivematrix manner and an active matrix manner.

The buffer layer may have a multilayer structure including a siliconnitride film and a silicon oxide film, and the silicon nitride film maycontact the first LED sub-unit, and the silicon oxide film may contactthe first adhesive layer.

The LED stack may further include a distributed Bragg reflectorinterposed to between the silicon nitride film and the silicon oxidefilm.

The first, second, and third LED sub-units may be configured to emit redlight, green light, and blue light, respectively.

A display apparatus may include a substrate including a circuit boardincluding a thin film transistor, and a plurality of pixels disposed onthe substrate, in which at least some of the pixels may include thelight emitting diode stack according to exemplary embodiments.

The display apparatus may further include a plurality of metal bondingmaterials disposed in the first adhesive layer.

The display apparatus may further include electrode pads disposed on thesubstrate, and first electrode pads disposed under the first LEDsub-unit, in which each of the metal bonding materials may bond theelectrode pads of the substrate and the first electrode pads.

An empty space may be formed between the first adhesive layer and themetal bonding material.

The display apparatus may further include a second adhesive layerinterposed between the first LED sub-unit and the second LED sub-unit,and a third adhesive layer interposed between the second LED sub-unitand the third LED sub-unit, in which the second and third adhesivelayers may include the metal bonding materials.

The first, second, and third LED sub-units may be electrically connectedto the first electrode pads, n-type semiconductor layers of the first,second, and third LED sub-units may be electrically connected in commonto one of the first electrode pads, p-type semiconductor layers of thefirst, second, and third LED sub-units may be electrically connected tofirst electrode pads that are different from each other, respectively,the first, second, and third LED sub-units may be configured to beindependently drivable, light generated in the first LED sub-unit may beconfigured to be transmitted through the second and third LED sub-unitsand emitted to the outside, and light generated in the second LEDsub-unit may be configured to be transmitted through the third LEDsub-unit and emitted to the outside.

The n-type semiconductor layers of the first, second, and third LEDsub-units may be grounded.

The display apparatus may further include connectors electricallyconnecting the second LED sub-unit and the third LED sub-unit to thefirst electrode pads.

The connectors may pass through at least one of the first LED sub-unitand the second LED sub-unit, and are disposed under the third LEDsub-unit.

The connectors may include a first connector, a second connector, and athird connector that pass through the first LED sub-unit, the firstconnector may be electrically connected to the n-type semiconductorlayer of the first LED sub-unit, and the second and third connectors maybe electrically insulated from the first LED sub-unit, and electricallyconnected to the first electrode pads, respectively.

The connectors may further include a fourth connector and a fifthconnector that pass through the second LED sub-unit, the fourthconnector may electrically connect the n-type semiconductor layer of thesecond LED sub-unit to the first connector, and the fifth connector maybe electrically insulated from the second LED sub-unit and is connectedto the third connector.

The display apparatus may further include a barrier separating thepixels from each other.

The display apparatus may further include a first color filterinterposed between the first LED sub-unit and the second LED sub-unit,and configured to transmit light generated in the first LED sub-unit andreflect light generated in the second LED sub-unit, and a second colorfilter interposed between the second LED sub-unit and the third LEDsub-unit, and configured to transmit light generated in the first andsecond LED sub-units and reflect light generated in the third LEDsub-unit.

Upper and lower surfaces of the metal bonding materials may besubstantially flat, and side surfaces of the metal bonding materials maybe substantially curved.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain theinventive concepts.

FIG. 1 is a cross-sectional view of a light emitting stacked structureaccording to an exemplary embodiment.

FIG. 2 is a cross-sectional view of a light emitting stacked structureincluding a wiring part according to an exemplary embodiment.

FIG. 3 is a cross-view of a light emitting stacked structure accordingto an exemplary embodiment.

FIG. 4 is a plan view of a display device according to an exemplaryembodiment.

FIG. 5 is an enlarged plan view of portion P1 of FIG. 4.

FIG. 6 is a structural diagram of a display device according to anexemplary embodiment.

FIG. 7 is a circuit diagram of one pixel of a passive type displaydevice according to an exemplary embodiment.

FIG. 8 is a circuit diagram of one pixel of an active type displaydevice according to an exemplary embodiment.

FIG. 9 is a plan view of a pixel according to an exemplary embodiment.

FIG. 10A and FIG. 10B are cross-sectional views taken along lines I-I′and II-II′ in FIG. 10, respectively.

FIG. 11, FIG. 13, FIG. 15, FIG. 17, FIG. 19, FIG. 21 are plan viewsillustrating a method of manufacturing a pixel on a substrate accordingto an exemplary embodiment.

FIG. 12A and FIG. 12B are cross-sectional views taken along line I-I′and line II-II′ of FIG. 11, respectively.

FIG. 14A and FIG. 14B are cross-sectional views taken along line I-I′and line II-II′of FIG. 13, respectively.

FIG. 16A and FIG. 16B are cross-sectional views taken along line I-I′and line II-II′ of FIG. 15, respectively.

FIG. 18A and FIG. 18B are cross-sectional views taken along line I-I′and line II-II′ of FIG. 17, respectively.

FIG. 20A and FIG. 20B are cross-sectional views taken along line I-I′and line II-II′ of FIG. 19, respectively.

FIG. 22A and FIG. 22B are cross-sectional views taken along line I-I′and line II-II′ of FIG. 21, respectively.

FIG. 23 is a cross-sectional view of a light emitting stacked structureaccording to an exemplary embodiment.

FIG. 24 is a cross-sectional view illustrating a light emitting stackedstructure including a wiring part according to an exemplary embodiment.

FIG. 25 is a plan view of a light emitting stacked structure accordingto an exemplary embodiment.

FIG. 26 is a cross-sectional view taken along line III-III′ of FIG. 25.

FIG. 27, FIG. 29, FIG. 31, and FIG. 33 are plan views illustrating amethod of manufacturing an epitaxial stack according to an exemplaryembodiment.

FIG. 28 is a cross-sectional view taken along line III-III- of FIG. 27.

FIG. 30A and FIG. 30B are cross-sectional views taken along lineIII-III′ of FIG. 29, respectively, according to exemplary embodiments.

FIG. 32A and FIG. 32B are cross-sectional views taken along lineIII-III′ of FIG. 31, respectively, according to exemplary embodiments.

FIG. 34 is a cross-sectional view taken along line III-III- of FIG. 33.

FIG. 35 is a plan view schematically illustrating a display apparatusaccording to an exemplary embodiment.

FIG. 36 is a schematic cross-sectional of a light-emitting diode (LED)pixel for a display according to an exemplary embodiment.

FIG. 37A and FIG. 37B are circuit diagrams of a display apparatusaccording to exemplary embodiments.

FIG. 38A and FIG. 38B are an enlarged plan view and an enlarged bottomview of one pixel of a display apparatus according to an exemplaryembodiment, respectively.

FIG. 39A is a schematic cross-sectional view taken along line A-A ofFIG. 38A.

FIG. 39B is a schematic cross-sectional view taken along line B-B ofFIG. 38A.

FIG. 39C is a schematic cross-sectional view taken along line C-C ofFIG. 38A.

FIG. 39D is a schematic cross-sectional view taken along line D-D ofFIG. 38A.

FIG. 40A, FIG. 41A, FIG. 42A, FIG. 43A, FIG. 44A, FIG. 45A, FIG. 46A,and FIG. 47B are plan views schematically illustrating a method ofmanufacturing a display apparatus according to an exemplary embodiment.

FIG. 40B, FIG. 41B, FIG. 42B, FIG. 43B, FIG. 44B, FIG. 45B, FIG. 46B,and FIG. 47B are cross-sectional view taken along line E-E of FIG. 40A,FIG. 41A, FIG. 42A, FIG. 43A, FIG. 44A, FIG. 45A, FIG. 46A, and FIG.47B, respectively.

FIG. 48 is a schematic cross-sectional view of an LED pixel for adisplay according to another exemplary embodiment.

FIG. 49 is an enlarged plan view of one pixel of a display apparatusaccording to an exemplary embodiment.

FIG. 50A and FIG. 50B are cross-sectional views taken along lines G-Gand H-H of FIG. 49, respectively.

FIG. 51 is a schematic plan view of a display apparatus according to anexemplary embodiment.

FIG. 52A is a schematic plan view of a light emitting device accordingto an exemplary embodiment.

FIG. 52B and FIG. 52C are schematic cross-sectional views taken alongline A-A and line B-B of FIG. 52A, respectively.

FIG. 53, FIG. 54, FIG. 55, FIG. 56, FIG. 57A, FIG. 57B, FIG. 58A, FIG.58B, FIG. 59A, FIG. 59B, FIG. 60A, FIG. 60B, FIG. 61A, FIG. 61B, FIG.62A, FIG. 62B, FIG. 63A, FIG. 63B, FIG. 64A, and FIG. 64B are schematicplan views and cross-sectional views illustrating a method ofmanufacturing a light emitting device according to an exemplaryembodiment.

FIG. 65 is a schematic cross-sectional view of a light emitting diode(LED) stack for a display according to an exemplary embodiment.

FIG. 66A, FIG. 66B, FIG. 66C, FIG. 66D, FIG. 66E, and FIG. 66F areschematic cross-sectional views illustrating a method for manufacturinga light emitting diode stack for a display according to an exemplaryembodiment.

FIG. 67 is a schematic circuit diagram of a display apparatus accordingto an exemplary embodiment.

FIG. 68 is a schematic plan view of a display apparatus according to anexemplary embodiment.

FIG. 69 is an enlarged plan view of one pixel of the display apparatusof FIG. 68.

FIG. 70 and FIG. 71 are schematic cross-sectional views taken along lineA-A and line B-B of FIG. 69, respectively.

FIG. 72A, FIG. 72B, FIG. 72C, FIG. 72D, FIG. 72E, FIG. 72F, FIG. 72G,and FIG. 72H are schematic plan views illustrating a method formanufacturing a display apparatus according to an exemplary embodiment.

FIG. 73 is a cross-sectional view of a light emitting stacked structureaccording to an exemplary embodiment.

FIG. 74A and FIG. 74B are cross-sectional views of a light emittingstacked structure according to exemplary embodiments.

FIG. 75 is a cross-sectional view of a light emitting stacked structureincluding a wiring part according to an exemplary embodiment.

FIG. 76 is a cross-view of a light emitting stacked structure accordingto an exemplary embodiment.

FIG. 77 is a plan view illustrating a display device according to anexemplary embodiment.

FIG. 78 is an enlarged plan view illustrating portion P1 of FIG. 77.

FIG. 79 is a structural diagram of a display device according to anexemplary embodiment.

FIG. 80 is a circuit diagram of one pixel of a passive type displaydevice according to an exemplary embodiment.

FIG. 81 is a schematic circuit diagram of one pixel of an active typedisplay device according to an exemplary embodiment.

FIG. 82 is a plan view of a pixel according to an exemplary embodiment.

FIG. 83A and FIG. 83B are cross-sectional views taken along lines I-I′and II-II′ of FIG. 82, respectively.

FIG. 84A, FIG. 84B, and FIG. 84C are cross-sectional views take alongline I-I′ of FIG. 82 according to an exemplary embodiment.

FIG. 85, FIG. 87, FIG. 89, FIG. 91, FIG. 93, FIG. 95, and FIG. 97 areplan views illustrating a method of manufacturing a pixel on a substrateaccording to an exemplary embodiment.

FIG. 86A and FIG. 86B are cross-sectional views taken along line I-I′and line II-II′ of FIG. 85, respectively.

FIG. 88A and FIG. 88B are cross-sectional views taken along line I-I′and line II-II′ of FIG. 87, respectively.

FIG. 90A and FIG. 90B are cross-sectional views taken along line I-I′and line II-II′ of FIG. 89, respectively.

FIG. 92A and FIG. 92B are cross-sectional views taken along line I-I′and line II-II′ of FIG. 91, respectively.

FIG. 94A and FIG. 94B are cross-sectional views taken along line I-I′and line II-II′ of FIG. 93, respectively.

FIG. 96A and FIG. 96B are cross-sectional views taken along line I-I′and line II-II′ of FIG. 95, respectively.

FIG. 98A and FIG. 98B are cross-sectional views taken along line I-I′and line II-II′ of FIG. 97, respectively.

FIG. 99 is a schematic plan view of a display apparatus according to anexemplary embodiment.

FIG. 100A is a partial cross-sectional view of the display apparatus ofFIG. 1.

FIG. 100B is a schematic circuit diagram of a display apparatusaccording to an exemplary embodiment.

FIG. 101A, FIG. 101B, FIG. 101C, FIG. 101D, FIG. 101E, FIG. 102A, FIG.102B, FIG. 102C, FIG. 102D, FIG. 102E, FIG. 103A, FIG. 103B, FIG. 103C,FIG. 103D, FIG. 104A, FIG. 104B, FIG. 104C, FIG. 104D, FIG. 105A, FIG.105B, FIG. 105C, FIG. 105D, FIG. 106A, FIG. 106B, and FIG. 107 areschematic plan views and cross-sectional views illustrating amanufacturing method of the display apparatus according to an exemplaryembodiment.

FIG. 108A, FIG. 108B, and FIG. 108C are schematic partialcross-sectional views of a metal bonding material according to exemplaryembodiments.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various exemplary embodiments or implementations of theinvention. As used herein “embodiments” and “implementations” areinterchangeable words that are non-limiting examples of devices ormethods employing one or more of the inventive concepts disclosedherein. It is apparent, however, that various exemplary embodiments maybe practiced without these specific details or with one or moreequivalent arrangements. In other instances, well-known structures anddevices are shown in block diagram form in order to avoid unnecessarilyobscuring various exemplary embodiments. Further, various exemplaryembodiments may be different, but do not have to be exclusive. Forexample, specific shapes, configurations, and characteristics of anexemplary embodiment may be used or implemented in another exemplaryembodiment without departing from the inventive concepts.

Unless otherwise specified, the illustrated exemplary embodiments are tobe understood as providing exemplary features of varying detail of someways in which the inventive concepts may be implemented in practice.Therefore, unless otherwise specified, the features, components,modules, layers, films, panels, regions, and/or aspects, etc.(hereinafter individually or collectively referred to as “elements”), ofthe various embodiments may be otherwise combined, separated,interchanged, and/or rearranged without departing from the inventiveconcepts.

The use of cross-hatching and/or shading in the accompanying drawings isto generally provided to clarify boundaries between adjacent elements.As such, neither the presence nor the absence of cross-hatching orshading conveys or indicates any preference or requirement forparticular materials, material properties, dimensions, proportions,commonalities between illustrated elements, and/or any othercharacteristic, attribute, property, etc., of the elements, unlessspecified. Further, in the accompanying drawings, the size and relativesizes of elements may be exaggerated for clarity and/or descriptivepurposes. When an exemplary embodiment may be implemented differently, aspecific process order may be performed differently from the describedorder. For example, two consecutively described processes may beperformed substantially at the same time or performed in an orderopposite to the described order. Also, like reference numerals denotelike elements.

When an element, such as a layer, is referred to as being “on,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, connected to, or coupled to the other element or layer orintervening elements or layers may be present. When, however, an elementor layer is referred to as being “directly on,” “directly connected to,”or “directly coupled to” another element or layer, there are nointervening elements or layers present. To this end, the term“connected” may refer to physical, electrical, and/or fluid connection,with or without intervening elements. Further, the D1-axis, the D2-axis,and the D3-axis are not limited to three axes of a rectangularcoordinate system, such as the x, y, and z-axes, and may be interpretedin a broader sense. For example, the D1-axis, the D2-axis, and theD3-axis may be perpendicular to one another, or may represent differentdirections that are not perpendicular to one another. For the purposesof this disclosure, “at least one of X, Y, and Z” and “at least oneselected from the group consisting of X, Y, and Z” may be construed as Xonly, Y only, Z only, or any combination of two or more of X, Y, and Z,such as, for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Although the terms “first,” “second,” etc. may be used herein todescribe various types of elements, these elements should not be limitedby these terms. These terms are used to distinguish one element fromanother element. Thus, a first element discussed below could be termed asecond element without departing from the teachings of the disclosure.

Spatially relative terms, such as “beneath,” “below,” “under,” “lower,”“above,” “upper,” “over,” “higher,” “side” (e.g., as in “sidewall”), andthe like, may be used herein for descriptive purposes, and, thereby, todescribe one elements relationship to another element(s) as illustratedin the drawings. Spatially relative terms are intended to encompassdifferent orientations of an apparatus in use, operation, and/ormanufacture in addition to the orientation depicted in the drawings. Forexample, if the apparatus in the drawings is turned over, elementsdescribed as “below” or “beneath” other elements or features would thenbe oriented “above” the other elements or features. Thus, the exemplaryterm “below” can encompass both an orientation of above and below.Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90degrees or at other orientations), and, as such, the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof. It is also noted that, as used herein, the terms“substantially,” “about,” and other similar terms, are used as terms ofapproximation and not as terms of degree, and, as such, are utilized toaccount for inherent deviations in measured, calculated, and/or providedvalues that would be recognized by one of ordinary skill in the art.

Various exemplary embodiments are described herein with reference tosectional and/or exploded illustrations that are schematic illustrationsof idealized exemplary embodiments and/or intermediate structures. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should notnecessarily be construed as limited to the particular illustrated shapesof regions, but are to include deviations in shapes that result from,for instance, manufacturing. In this manner, regions illustrated in thedrawings may be schematic in nature and the shapes of these regions maynot reflect actual shapes of regions of a device and, as such, are notnecessarily intended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and should not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

Hereinafter, exemplary embodiments will be described in detail withreference to the accompanying drawings. As used herein, a light emittingdevice or a light emitting diode according to exemplary embodiments mayinclude a micro LED, which has a surface area less than about 10,000square μm as known in the art. In other exemplary embodiments, the microLED's may have a surface area of less than about 4,000 square μm, orless than about 2,500 square μm, depending upon the particularapplication.

FIG. 1 is a cross-sectional view of a light emitting stacked structureaccording to an exemplary embodiment.

Referring to FIG. 1, a light emitting stacked structure according to anexemplary embodiment includes a plurality of sequentially stackedepitaxial stacks, and optically non-transmissive films covering sides ofthe epitaxial stacks. The plurality of epitaxial stacks is provided onthe substrate 10. The substrate 10 may substantially have a plate shapeincluding an upper surface and a lower surface. As used herein, a lightemitting stacked structure according to exemplary embodiments mayinclude a micro light emitting structure or a micro LED, which generallyhas a form factor of about 200 square micrometers or less, or about 100square micrometers or less in surface area, as is known in the art.

A plurality of epitaxial stacks may be mounted on the upper surface ofthe substrate 10, and the substrate 10 may be provided in various forms.The substrate 10 may be formed of an insulating material. Examples ofthe material of the substrate 10 may include glass, quartz, silicon,organic polymer, organic-inorganic composite, or others. However, theinventive concepts are not limited a particular material of thesubstrate 10, as long as it has an insulation property. In an exemplaryembodiment, the substrate 10 may further include a wiring part that mayprovide a light emitting signal and a common voltage to the respectiveepitaxial stacks. In particular, when each of the epitaxial stacks isdriven in an active matrix type, a driving element including a thin filmtransistor may be further disposed on the substrate 10 in addition tothe wiring part. To this end, the substrate 10 may be provided as aprinted circuit board 10 or as a composite substrate 10 having a wiringpart and/or a drive element formed on glass, silicon, quartz, organicpolymer, or organic/inorganic composite.

The epitaxial stacks are sequentially stacked on the upper surface ofthe substrate 10, and may respectively emit light. In an exemplaryembodiment, two or more epitaxial stacks may be provided to emit lightof different wavelength bands from each other, respectively. Moreparticularly, a plurality of epitaxial stacks may be provided,respectively having different energy bands from each other. Theepitaxial stack on the substrate 10 may be sequentially disposed overone another. According to an exemplary embodiment, the epitaxial stackmay include first, second, and third epitaxial stacks 20, 30, and 40sequentially disposed on the substrate 10.

Each of the epitaxial stacks may emit light towards the front side ofthe substrate 10. Light emitted from one epitaxial stack may passthrough another epitaxial stack located in the light path, and travelsto the front direction. For example, the front direction may correspondto a direction along which the first to third epitaxial stacks 20, 30,and 40 are stacked, as shown in FIG. 1.

Each of the epitaxial stacks may emit a color light of a visible lightband of various wavelength bands. For example, light emitted from thelowermost epitaxial stack may be a color light having the longestwavelength (e.g., the lowest energy band), and the wavelength of thelight emitted the epitaxial stacks may become shorter along a directionaway from the substrate 10. Light emitted from the uppermost epitaxialstack may have a color light having the shortest wavelength (e.g., thehighest energy band). For example, the first epitaxial stack 20 may emitthe first color light L1, the second epitaxial stack 30 may emit thesecond color light L2, and the third epitaxial stack 40 may emit thethird color light L3. The first to third color light L1, L2, and L3 maycorrespond to different color light from each other, and the first tothird color light L1, L2, and L3 may be color light of differentwavelength bands from each other which have sequentially decreasingwavelengths. In particular, the first to third color light L1, L2, andL3 may have different wavelength bands from each other, and the colorlight may be a shorter wavelength band (e.g., a higher energy) in theorder of the first color light L1 to the third color light L3. However,the inventive concepts are not limited thereto, and the wavelength oflight emitted from each epitaxial stack may be variously modified.

In an exemplary embodiment, the first color light L1 may be red light,the second color light L2 may be green light, and the third color lightL3 may be blue light.

Hereinafter, in addition to the front direction and the back directionmentioned above, the “front” direction of the substrate 10 will bereferred to as the “upper” direction, and “back” direction of thesubstrate 10 will be referred to as the “lower” direction. The terms“upper” or “lower” refer to relative directions, which may varyaccording to the placement and the direction of the light emittingstacked structure.

Each of the epitaxial stacks emits light in an upper direction, and eachof the epitaxial stacks transmits most of light emitted from theunderlying epitaxial stacks. In particular, light emitted from the firstepitaxial stack 20 passes through the second epitaxial stack 30 and thethird epitaxial stack 40, and travels to the front direction. Lightemitted from the second epitaxial stack 30 passes through the thirdepitaxial stack 40 and travels to the front direction. To this end, atleast some, or desirably, all of the epitaxial stacks other than thelowermost epitaxial stack 20 may be composed of an opticallytransmissive material. As used herein, the material being “opticallytransmissive” may refer to transmitting the entire light or transmittingat least a portion of light having a predetermined wavelength. In anexemplary embodiment, each of the epitaxial stacks may transmit about60% or more of light emitted from the epitaxial stack disposedthereunder, or about 80% or more in another exemplary embodiment, orabout 90% or more in yet another exemplary embodiment.

An optically non-transmissive (substantially, total reflective) film 80may be provided on the sides of the epitaxial stacks, more particularly,on the sides of the first to third epitaxial stacks 20, 30, and 40. Theoptically non-transmissive film 80 may substantially cover the entiresides of the first to third epitaxial stacks 20, 30, and 40 to preventlight from being emitted therefrom.

The optically non-transmissive film 80 is not particularly limited aslong as it blocks light transmission by absorbing or reflecting light.In an exemplary embodiment, the optically non-transmissive film 80 maybe a distributed Bragg reflector (DBR), a metal reflective film formedon an insulating film, or an organic polymer film having a black color.When a metal reflective film is used as the optically non-transmissivefilm, the metal reflective film may be in a floating state that iselectrically isolated from the components within other pixels. The metalreflective film may also be provided in a form of an extension from oneof the components within other pixels, for example, as an extension fromone of the other lines, in which case the metal reflective film isprovided within a range that is not electrically connected to the otherconductive components.

In an exemplary embodiment, the optically non-transmissive film 80 mayhave a single or a multi-layered film structure, and may include two ormore different types of materials when provided as a multilayer film. Inan exemplary embodiment, the optically non-transmissive film 80 may beformed by depositing two or more insulating films of differentrefractive indices from each other. For example, the opticallynon-transmissive film 80 may be formed by stacking a material having alow refractive index and a material having a high refractive index insequence, or alternatively by stacking insulating films having differentrefractive indices from each other. Materials having differentrefractive indices may include SiO₂ or SiN_(x), but the inventiveconcepts are not limited thereto. The wavelength of light absorbed orreflected by the optically non-transmissive film 80 may be controlled byway of changing the materials thereof, the thickness of stack, thefrequency of stacking, or the like.

In an exemplary embodiment, the optically non-transmissive film 80 maybe provided on the sides of the pixels to prevent the phenomenon inwhich light emitted from a certain pixel affects adjacent pixels, or thephenomenon in which color is mixed with light emitted from the adjacentpixels. Accordingly, each of the epitaxial stacks has a side in atapered shape to facilitate depositing of the optically non-transmissivefilm 80. In particular, the side of each of the epitaxial stacks mayhave an inclined shape relative to one surface of the substrate 10(e.g., an upper surface or lower surface of the substrate).

In an exemplary embodiment, the side of each of the epitaxial stacks hasan inclined shape relative to one surface of the substrate 10. Accordingto an exemplary embodiment, an angle between the sides of the first tothird epitaxial stacks 20, 30, and 40 and the one surface of thesubstrate 10 may be greater than about 0 degrees and less than about 90degrees in a cross-sectional view. For example, when angles between thesides of the first to third epitaxial stacks 20, 30, and 40 and the onesurface of the substrate 10 is first to third angles θ₁, θ₂, and θ₃, thefirst to third angles θ₁, θ₂, and θ₃ may have values in a range fromabout 45 degrees to about 85 degrees, respectively.

When the sides of the first to third epitaxial stacks 20, 30 and 40 havea predetermined inclination as described above, it may be relativelyeasy to form the optically non-transmissive film 80. Further, when eachof the epitaxial stacks has a tapered shape at a predetermined angle,the light reflection effect by the optically non-transmissive film 80may be maximized or substantially increased. The opticallynon-transmissive film 80 may be formed using physical and/or chemicalvapor deposition, but when the sides of the first to third epitaxialstacks 20, 30, and 40 are perpendicular or nearly perpendicular to thesubstrate 10 surface, it may be difficult to sufficiently cover thesides of the first to third epitaxial stacks 20, 30, and 40 with theoptically non-transmissive film 80. In particular, if the sides of thefirst to third epitaxial stacks 20, 30, and 40 are perpendicular to ornearly perpendicular to the substrate 10 surface, even when theoptically non-transmissive film 80 is formed by physical and/or chemicalvapor deposition, the thickness of the optically non-transmissive filmformed on the sides may be thinner than the thickness of the opticallynon-transmissive film 80 formed on the upper surface, and there is ahigh possibility that the optically non-transmissive film 80 formed onthe side have cracks. As such, the side portions of the first to thirdepitaxial stacks 20, 30, and 40 may not be sufficiently covered by theoptically non-transmissive film 80, which may cause light leakage fromthe epitaxial stacks.

According to an exemplary embodiment, when the side of each of the firstto third epitaxial stacks 20, 30, and 40 and the one surface of thesubstrate 10 are at an angle of inclination between about 45 degrees andabout 85 degrees, the optically non-transmissive film 80 may besufficiently formed on each side of the first to third epitaxial stacks20, 30, and 40. Further, when each of the epitaxial stacks has a taperedshape at a predetermined angle, the light reflection effect by theoptically non-transmissive film 80 may be maximized or substantiallyincreased. As such, the angles between the sides of each of the first tothird epitaxial stacks 20, 30, and 40 and the one surface of thesubstrate 10 may be the same or different from each other. The anglesbetween the sides of the first to third epitaxial stacks 20, 30, and 40and the one surface of the substrate 10 may be determined inconsideration of the materials of each of the epitaxial stacks, theetching rate during patterning, the degree of reflection of lightemitted from each of the epitaxial stacks, or others. For example, amongthe angles formed between the sides of the first to third epitaxialstacks 20, 30, and 40 and the one surface of the substrate 10, the firstangle θ₁, the second angle θ₂, and the third angle θ₃ may be differentfrom one another, or alternatively, the second angle θ₂ and the thirdangle θ₃ may be the same as each other and different from the firstangle θ₁. In an exemplary embodiment, the angle between the sides ofeach of the first to third epitaxial stacks 20, 30, and 40 and the onesurface of the substrate 10 may be determined in consideration of thedifference of wavelength of light emitted. For example, the angles maybe determined to allow the highest total internal reflection to occurwhen light emitted from each of the epitaxial stacks travels to thedirection of the sides.

In an exemplary embodiment, the optically non-transmissive film 80 maybe provided only on the sides of the epitaxial stacks, but the inventiveconcepts are not limited thereto. For example, the opticallynon-transmissive film 80 may extend over a portion of the upper surfaceof the uppermost epitaxial stack to cover at least a portion of theupper surface of the uppermost epitaxial stack where emission of lightis not desired. More particularly, as shown in FIG. 1, the opticallynon-transmissive film 80 has a window for exposing the upper surface ofthe epitaxial stack at the top corresponding to a region where emissionof light is desired. As used herein, a light emitting region that isvisible to the user may be referred to as a “light emitting region(EA)”, and the remaining light emitting region may be referred to as a“peripheral region”. The optically non-transmissive film 80 has a windowin the light emitting region, and may cover a portion of the uppersurface of the third epitaxial stack 40 and the entire sides in theperipheral region except for the light emitting region. Accordingly, theoptically non-transmissive film 80 may cover a portion of an edge of theupper surface of the epitaxial stack to reduce the directivity angle ofthe emitted light, and thus, interference with light from the adjacentlight emitting stacked structures may be minimized.

In the light emitting stacked structure according to an exemplaryembodiment, signal lines for applying emitting signals to the respectiveepitaxial stacks may be independently connected. Accordingly, therespective epitaxial stacks can be independently driven, and the lightemitting stacked structure can implement various colors according towhether light is emitted from each of the epitaxial stacks. In addition,the epitaxial stacks that may emit light of different wavelengths fromeach other are overlapped vertically on one another, and thus, can beformed in a narrow area. In addition, since the sides of the epitaxialstacks are inclined, it is possible to easily form the non-transmissivefilm 80 with a sufficient thickness, and the non-transmissive film 80can prevent the phenomenon in which light emitted from a certain pixelaffects the adjacent pixels, or the phenomenon in which color is mixedwith the light emitted from the adjacent pixels.

FIG. 2 is a cross-sectional view of a light emitting stacked structureincluding a wiring part according to an exemplary embodiment. In FIG. 2,the inclined shapes of each of the epitaxial stacks and the insulatingfilms shown in FIG. 1 are omitted.

Referring to FIG. 2, in a light emitting stacked structure according toan exemplary embodiment, each of the first to third epitaxial stacks 20,30, and 40 may be provided on the substrate 10, via the first to thirdadhesive layers 61, 63, and 65 interposed therebetween. The firstadhesive layer 61 may include a conductive or non-conductive material.The first adhesive layer 61 may have conductivity in some regions whenit needs to be electrically connected to the substrate 10 providedthereunder. The first adhesive layer 61 may also include a transparentor opaque material. In an exemplary embodiment, when the substrate 10 isprovided with an opaque material and has a wiring part or the likeformed thereon, the first adhesive layer 61 may include an opaquematerial, for example, a light absorbing material. For the lightabsorbing material that forms the first adhesive layer 61, variouspolymer adhesives may be used, including, for example, an epoxy-basedpolymer adhesive.

The second and third adhesive layers 63 and 65 may include anon-conductive material and may also include an optically transmissivematerial. For example, an optically clear adhesive may be used for thesecond and third adhesive layers 65. The material for forming the secondand third adhesive layers 63 and 65 is not particularly limited, as longas it is optically transparent and is capable of attaching each of theepitaxial stacks stably. For example, the second and third adhesivelayers 63 and 65 may be formed of an organic material including anepoxy-based polymer such as SU-8, various resists, parylene, poly(methylmethacrylate) (PMMA), benzocyclobutene (BCB), spin on glass (SOG), orothers, and inorganic material such as silicon oxide, aluminum oxide, orthe like. According to an exemplary embodiment, a conductive oxide mayalso be used as an adhesive layer, in which case the conductive oxidemay be insulated from other components. When an organic material is usedas the adhesive layer, the organic material may be applied to theadhesive surface and then bonded at a high temperature and a highpressure in a vacuum state. When an inorganic material is used as theadhesive layer, the inorganic material may be deposited on the adhesivesurface and then planarized by chemical-mechanical planarization (CMP)or the like, after which the surface is subjected to the plasmatreatment and then bonded by bonding under a high vacuum.

Each of the first to third epitaxial stacks 20, 30, and 40 includesp-type semiconductor layers 25, 35, and 45, active layers 23, 33, and43, and n-type semiconductor layers 21, 31, and 41, which aresequentially disposed.

According to an exemplary embodiment, the p-type semiconductor layer 25,the active layer 23, and the n-type semiconductor layer 21 of the firstepitaxial stack 20 may include a semiconductor material that emits redlight. However, the inventive concepts are not limited to a particularcolor of light emitted from the first epitaxial stack 20.

Examples of a semiconductor material that emits red light may includealuminum gallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP),aluminum gallium indium phosphide (AlGaInP), gallium phosphide (GaP), orothers. However, the semiconductor material that emits red light is notlimited thereto, and various other materials may be used.

A first p-type contact electrode 25 p may be provided under the p-typesemiconductor layer 25 of the first epitaxial stack 20. The first p-typecontact electrode 25 p of the first epitaxial stack 20 may be a singlelayer or a multi-layer metal. For example, the first p-type contactelectrode 25 p may include various materials including metals, such asAl, Ti, Cr, Ni, Au, Ag, Ti, Sn, Ni, Cr, W, Cu, or others, or alloysthereof. The first p-type contact electrode 25 p may include metalhaving a high reflectivity, and accordingly, since the first p-typecontact electrode 25 p is formed of a metal having high reflectivity, itis possible to increase the emission efficiency of light emitted fromthe first epitaxial stack 20 in the upper direction.

The second epitaxial stack 30 includes a p-type semiconductor layer 35,an active layer 33, and an n-type semiconductor layer 31, which aresequentially disposed. The p-type semiconductor layer 35, the activelayer 33, and the n-type semiconductor layer 31 may include asemiconductor material that emits green light. However, the inventiveconcepts are not limited to a particular color of light emitted from thesecond epitaxial stack 30.

Examples of materials for emitting green light include indium galliumnitride (InGaN), gallium nitride (GaN), gallium phosphide (GaP),aluminum gallium indium phosphide (AlGaInP), and aluminum galliumphosphide (AlGaP). However, the semiconductor material that emits greenlight is not limited thereto, and various other materials may be used.

A second p-type contact electrode 35 p is provided under the p-typesemiconductor layer 35 of the second epitaxial stack 30. The secondp-type contact electrode 35 p is provided between the first epitaxialstack 20 and the second epitaxial stack 30, or specifically, between thesecond adhesive layer 63 and the second epitaxial stack 30.

The third epitaxial stack 40 includes a p-type semiconductor layer 45,an active layer 43, and an n-type semiconductor layer 41, which aresequentially disposed. The p-type semiconductor layer 45, the activelayer 43, and the n-type semiconductor layer 41 may include asemiconductor material that emits blue light. However, the inventiveconcepts are not limited to a particular color of light emitted from thethird epitaxial stack 40.

The examples of the materials that emit blue light may include galliumnitride (GaN), indium gallium nitride (InGaN), zinc selenide (ZnSe), orothers. However, the semiconductor material that emits blue light is notlimited thereto, and various other materials may be used.

A third p-type contact electrode 45 p is provided under the p-typesemiconductor layer 45 of the third epitaxial stack 40. The third p-typecontact electrode 45 p is provided between the second epitaxial stack 30and the third epitaxial stack 40, or specifically, between the thirdadhesive layer 65 and the third epitaxial stack 40.

In FIG. 2, although the n-type semiconductor layers 21, 31, and 41 andthe p-type semiconductor layers 25, 35, and 45 of the first to thirdepitaxial stacks 20, 30, and 40 are each shown as a single layer, theinventive concepts are not limited thereto, and these layers may bemultilayers and may also include superlattice layers. In addition, theactive layers of the first to third epitaxial stacks 20, 30, and 40 mayinclude a single quantum well structure or a multi-quantum wellstructure.

In an exemplary embodiment, the second and third p-type contactelectrodes 35 p and 45 p may substantially cover the second and thirdepitaxial stacks 30 and 40. The second and third p-type contactelectrodes 35 p and 45 p may include a transparent conductive materialto transmit light from the epitaxial stack below. For example, each ofthe second and third p-type contact electrodes 35 p and 45 p may includea transparent conductive oxide (TCO). The transparent conductive oxidemay include tin oxide (SnO), indium oxide (InO₂), zinc oxide (ZnO),indium tin oxide (ITO), indium tin zinc oxide (ITZO) or the like. Thetransparent conductive compound may be deposited by the chemical vapordeposition (CVD), the physical vapor deposition (PVD), such as anevaporator, a sputter, or the like. The second and third p-type contactelectrodes 35 p and 45 p may be provided with a sufficient thickness soas to function as an etch stopper during the fabrication process whichwill be described in more detail below, for example, with a thickness ofabout 2000 angstroms to about 2 micrometers to the extent that thetransparency is satisfied.

In an exemplary embodiment, common lines may be connected to the firstto third p-type contact electrodes 25 p, 35 p, and 45 p. The common linemay be a line to which the common voltage is applied. In addition, thelight emitting signal lines may be connected to the n-type semiconductorlayers 21, 31, and 41 of the first to third epitaxial stacks 20, 30, and40, respectively. For example, a common voltage Sc may be applied to thefirst p-type contact electrode 25 p, the second p-type contact electrode35 p, and the third p-type contact electrode 45 p through the commonline, and light emitting signal is applied to the n-type semiconductorlayers 21, 31, and 41 of the first to third epitaxial stacks 20, 30, and40, thereby controlling the light emission of the first to thirdepitaxial stacks 20, 30, and 40. The light emitting signal may includefirst to third light emitting signals S_(R), S_(G), and S_(B)corresponding to the first to third epitaxial stacks 20, 30, and 40,respectively. In an exemplary embodiment, the first light emittingsignal S_(R) may be a signal corresponding to red light, the secondlight emitting signal S_(G) may be a signal corresponding to greenlight, and the third light emitting signal S_(B) may be a signalcorresponding to an emission of blue light.

According to the exemplary embodiment, the first to third epitaxialstacks 20, 30, and 40 may be driven according to a light emitting signalapplied to each of the epitaxial stacks. In particular, the firstepitaxial stack 20 is driven according to a first light emitting signalS_(R), the second epitaxial stack 30 is driven according to a secondlight emitting signal S_(G), and the third epitaxial stack 40 is drivenaccording to the third light emitting signal S_(B). In particular, thefirst, second, and third driving signals S_(R), S_(G), and S_(B) may beindependently applied to the first to third epitaxial stacks 20, 30, and40, such that each of the first to third epitaxial stacks 20, 30 and 40may be independently driven. The light emitting stacked structure mayfinally provide light of various colors by combining the first to thirdcolor light emitted upward from the first to third epitaxial stacks 20,30 and 40.

In FIG. 2, a common voltage is described as being applied to the p-typesemiconductor layers 25, 35, and 45 of the first to third epitaxialstacks 20, 30, and 40, and the light emitting signal is described asbeing applied to the n-type semiconductor layers 21, 31, and 41 of thefirst to third epitaxial stacks 20, 30, and 40, however, the inventiveconcepts are not limited thereto. In another exemplary embodiment, acommon voltage may be applied to the n-type semiconductor layers 21, 31,and 41 of the first to third epitaxial stacks 20, 30, and 40, and lightemitting signals may be applied to the p-type semiconductor layers 25,35, and 45 of the first to third epitaxial stacks 20, 30, and 40.

In this manner, the light emitting stacked structure of FIG. 2 mayimplement a color in a manner such that portions of different colorlight are provided on the overlapped region, rather than implementingdifferent color light on different planes spaced apart from each other.Accordingly, the light emitting stacked structure may advantageouslyhave compactness and integration of the light emitting element. Ingeneral, conventional light emitting elements emitting different colors,such as red, green, and blue light, are spaced apart from each other ona plane to realize full color. As such, each of the conventional lightemitting elements is generally arranged on a plane, occupying a largerarea. However, according to exemplary embodiments, it is possible torealize a full color in a remarkably smaller area by providing a stackedstructure having the portions of the light emitting elements that emitdifferent color light overlapped in a one region. Accordingly, it ispossible to manufacture a high-resolution device even in a small area.

In addition, conventional light emitting device may have a complexstructure and manufacturing thereof is also not easy, because theconventional light emitting device, including the conventional stackedlight emitting device, is manufactured by separately preparingrespective light emitting elements and then forming separate contactssuch as connecting by interconnection lines, or others, for each of thelight emitting elements. However, according to an exemplary embodiment,the light emitting stacked structure is formed by stacking multi-layersof epitaxial stacks sequentially on a single substrate 10, and thenforming contacts on the multi-layered epitaxial stacks and connecting bylines through a minimum process. In addition, as compared to theconventional manufacturing method of display devices in which lightemitting elements of individual colors are separately manufactured andmounted separately, according to exemplary embodiments, only a singlelight emitting stacked structure is mounted instead of a plurality oflight emitting elements, which significantly simplifies itsmanufacturing method.

The light emitting stacked structure according to an exemplaryembodiment may additionally employ various components to provide highpurity and color light of high efficiency. For example, a light emittingstacked structure according to an exemplary embodiment may furtherinclude a wavelength pass filter to block shorter wavelength light fromproceeding toward the epitaxial stack that emits relatively longerwavelength light.

In the following exemplary embodiments, differences from the exemplaryembodiments described above will be mainly described, in order to avoidredundancy.

FIG. 3 is a cross-sectional view of a light emitting stacked structureincluding a predetermined wavelength pass filter according to anexemplary embodiment. In FIG. 3, some components shown in FIGS. 1 and 2are omitted.

Referring to FIG. 3, a light emitting stacked structure according to anexemplary embodiment includes a first wavelength pass filter 71 disposedbetween the first epitaxial stack and the second epitaxial stack 30.

The first may selectively transmit a certain wavelength light. Inparticular, the first wavelength pass filter 71 may transmit a firstcolor light emitted from the first epitaxial stack 20 while block orreflect light other than the first color light. Accordingly, the firstcolor light emitted from the first epitaxial stack 20 may travel in anupper direction, while the second and third color light emitted from thesecond and third epitaxial stacks 30 and 40 are blocked from travelingtoward the first epitaxial stack 20 and be reflected or blocked by thefirst wavelength pass filter 71.

The second and third color light may be high-energy light, which have arelatively shorter wavelength than the first color light. As such, whenentering the first epitaxial stack 20, the second and third color lightmay induce additional light emission in the first epitaxial stack 20. Inan exemplary embodiment, however, the second and the third color lightare blocked from entering the first epitaxial stack 20 by the firstwavelength pass filter 71.

In an exemplary embodiment, a second wavelength pass filter 73 may alsobe provided between the second epitaxial stack 30 and the thirdepitaxial stack 40. The second wavelength pass filter 73 transmits thefirst color light and the second color light emitted from the first andsecond epitaxial stacks 20 and 30, while blocking or reflecting lightother than the first and second color light. Accordingly, the first andsecond color light emitted from the first and second epitaxial stacks 20and 30 may travel in the upper direction, while the third color lightemitted from the third epitaxial stack 40 is not allowed to travel in adirection toward the first and second epitaxial stacks 20 and 30, butreflected or blocked by the second wavelength pass filter 73.

As described above, the third color light may be a relativelyhigh-energy light which has a shorter wavelength than the first andsecond color light. As such, when entering the first and secondepitaxial stacks 20 and 30, the third color light may induce additionalemission in the first and second epitaxial stacks 20 and 30. In theexemplary embodiment, however, the second wavelength pass filter 73prevents the third light from entering the first and second epitaxialstacks 20 and 30.

The first and second wavelength pass filters 71 and 73 may be formed invarious shapes, but may be formed by alternately stacking insulatingfilms having different refractive indices. For example, the wavelengthof transmitted light may be determined by alternately stacking SiO₂ andTiO₂, and adjusting the thickness and number of stacking of SiO₂ andTiO₂. The insulating films having different refractive indices mayinclude SiO₂, TiO₂, HfO₂, Nb₂O₅, ZrO₂, Ta₂O₅, or the like.

In an exemplary embodiment, the first to third p-type contact electrodes25 p, 35 p, and 45 p, the first to third adhesive layers 61, 63, and 65,and the first and second wavelength pass filters 71 and 73 may bepatterned together in the same step of patterning one of the first tothird epitaxial stacks 20, 30 and 40, or alternatively, may be patternedin a separate step. For example, the above layers may be inclined atsubstantially the same or similar angle as the first to third epitaxialstacks 20, 30, and 40. FIG. 3 shows that the first to third p-typecontact electrodes 25 p, 35 p, and 45 p, the first to third adhesivelayers 61, 63, and 65, and the first and second wavelength pass filters71 and 73 are patterned at the same angle as the first to thirdepitaxial stacks 20, 30 and 40. However, the inventive concepts are notlimited thereto, and the inclination angles of the first to third p-typecontact electrodes 25 p, 35 p, and 45 p, the first to third adhesivelayers 61, 63, and 65 and the first and second wavelength pass filters71 and 73 may be formed differently from that of the first to thirdepitaxial stacks 20, 30, and 40, depending on the materials, conditionsfor patterning process, or the like of each of the first to third p-typecontact electrodes 25 p, 35 p, and 45 p, the first to third adhesivelayers 61, 63, and 65, and the first and second wavelength pass filters71 and 73.

The light emitting stacked structure according to an exemplaryembodiment may additionally employ various components to provide uniformlight of high efficiency. For example, a light emitting stackedstructure according to an exemplary embodiment may have variousirregularities on the light exit surface. For example, a light emittingstacked structure according to an exemplary embodiment may haveirregularities formed on an upper surface of at least one n-typesemiconductor layer of the first to third epitaxial stacks 20, 30, and40.

The irregularities of each of the epitaxial stacks may be selectivelyformed. For example, irregularities may be provided on the firstepitaxial stack 20, and irregularities may be provided on the first andthird epitaxial stacks 20 and 40, and irregularities may be provided onthe first to third epitaxial stacks 20, 30 and 40. The irregularities ofeach of the epitaxial stacks may be provided on an n-type semiconductorlayer corresponding to the emission surface of each of the epitaxialstacks.

The irregularities formed on the epitaxial stacks may increase lightemission efficiency, and may be provided in various forms such as apolygonal pyramid, a hemisphere, or planes with a surface roughness in arandom arrangement. The irregularities may be textured through variousetching processes or may be formed using a patterned sapphire substrate.

In an exemplary embodiment, the first to third color light from thefirst to third epitaxial stacks 20, 30, and 40 may have different lightintensities, and this difference in intensity may lead to differences invisibility. For example, the light emission efficiency may be improvedby selectively forming irregularities on the light exit surface of thefirst to third epitaxial stacks 20, 30 and 40, which results inreduction of the visibility differences between the first to third colorlight. The color light corresponding to red and/or blue color may havelower visibility than the green color, in which case the first epitaxialstack 20 and/or the third epitaxial stack 40 may be textured to decreasethe difference of visibility. Particularly, in the case of red colorlight, since light may be provided from the lowermost of the lightemitting stacks, light intensity may be small, and light efficiency maybe increased by forming irregularities on the upper surface thereof.

The light emitting stacked structure having the structure describedabove may be capable of expressing various colors, and thus may beemployed as a pixel in a display device. In the following exemplaryembodiments, a display device will be described as including the lightemitting stacked structure described above.

FIG. 4 is a plan view of a display device according to an exemplaryembodiment, and FIG. 5 is an enlarged plan view illustrating portion P1of FIG. 4.

Referring to FIGS. 4 and 5, the display device 100 according to anexemplary embodiment may displays any visual information such as text,video, photographs, two or three-dimensional images, or the like.

The display device 100 may have various shapes including a closedpolygon that includes a straight side, such as a rectangle, or a circle,an ellipse, or the like, or that includes a curved side, or asemi-circle or semi-ellipse that includes a combination of straight andcurved sides. In an exemplary embodiment, the display device will bedescribed as having substantially a rectangular shape.

The display device 100 has a plurality of pixels 110 for displayingimages. Each of the pixels 110 may be a minimum unit for displaying animage. Each pixel 110 includes the light emitting stacked structurehaving the structure described above, and may emit white light and/orcolor light.

In an exemplary embodiment, each pixel includes a first pixel 110 _(R)that emits red light, a second pixel 110 _(G) that emits green light,and a third pixel 110 _(B) that emits blue light. The first to thirdpixels 110 _(R), 110 _(G), and 110 _(B) may correspond to the first tothird epitaxial stacks 20, 30, and 40 of the light emitting stackedstructure described above, respectively.

The pixels 110 are arranged in a matrix. As used herein, pixels having amatrix arrangement may refer to that the pixels are arranged in a linealong the row or column, or that the pixels 110 are arranged generallyalong the rows and columns, with certain modifications in details, suchas the pixels 110 being arranged in a zigzag shape, for example.

FIG. 6 is a structural diagram of a display device according to anexemplary embodiment.

Referring to FIG. 6, a display device 100 according to an exemplaryembodiment includes a timing controller 350, a scan driver 310, a datadriver 330, a wiring part, and pixels. Each of the pixels may beindividually connected to the scan driver 310, the data driver 330, orthe like through a wiring part.

The timing controller 350 receives various control signals and imagedata necessary for driving a display device from outside (e.g., from asystem for transmitting image data). The timing controller 350rearranges the received image data and transmits the image data to thedata driver 330. In addition, the timing controller 350 generates scancontrol signals and data control signals necessary for driving the scandriver 310 and the data driver 330, and outputs the generated scancontrol signals and data control signals to the scan driver 310 and thedata driver 330.

The scan driver 310 receives scan control signals from the timingcontroller 350 and generates corresponding scan signals. The data driver330 receives data control signals and image data from the timingcontroller 350 and generates corresponding data signals.

The wiring part includes a plurality of signal lines. The wiring partspecifically includes scan lines 130 connecting the scan driver 310 andthe pixels, and data lines 120 connecting the data driver 330 and thepixels. The scan lines 130 may be connected to respective pixels, andaccordingly, the scan lines 130 that correspond to the respective pixelsare indicated as first to third scan lines 130 _(R), 130 _(G), and 130_(B) (hereinafter, collectively referred to as ‘130’).

In addition, the wiring part further includes lines connecting betweenthe timing controller 350 and the scan driver 310, the timing controller350 and the data driver 330, or other components, and transmitting thesignals.

The scan lines 130 provide the scan signals generated from the scandriver 310 to pixels. The data signals generated at the data driver 330is outputted to the data lines 120.

The pixels are connected to the scan lines 130 and data lines 120. Thepixels selectively emit light in response to the data signals providedfrom the data lines 120 when the scan signals are supplied from scanlines 130. For example, during each frame period, each of the pixelsemits light with the luminance corresponding to the input data signals.The pixels supplied with data signals corresponding to black luminancemay display black by emitting no light during the corresponding frameperiod.

In an exemplary embodiment, the pixels may be driven as either passiveor active type. When the display device is driven as the active type,the display device may be supplied with the first and second pixelpowers in addition to the scan signals and the data signals.

FIG. 7 is a circuit diagram of one pixel in a passive type displaydevice. The pixel may be one of the pixels, for example, one of R, G, Bpixels, and FIG. 7 shows the first pixel 110 _(R) as an example. Sincethe second and third pixels may be driven in substantially the samemanner as the first pixel, the circuit diagrams for the second and thirdpixels will be omitted to avoid redundancy.

Referring to FIG. 7, a first pixel 110 _(R) includes a light emittingelement 150 connected between a scan line 130 and a data line 120. Thelight emitting element 150 may correspond to the first epitaxial stack20. The first epitaxial stack 20 emits light with a luminancecorresponding to the magnitude of the applied voltage when a voltageequal to or higher than a threshold voltage is applied between thep-type semiconductor layer and the n-type semiconductor layer. Inparticular, the emission of the first pixel 110 _(R) may be controlledby controlling the voltages of the scan signal applied to the first scanline 130 _(R) and/or the data signal applied to the data line 120.

FIG. 8 is a circuit diagram illustrating a first pixel of an active typedisplay device.

When the display device is the active type, the first pixel 110 _(R) maybe further supplied with the first and second pixel powers (ELVDD andELVSS) in addition to the scan signal and the data signal.

Referring to FIG. 8, the first pixel 110 _(R) includes a light emittingelement 150 and a transistor part connected thereto.

The light emitting element 150 corresponds to the first epitaxial stack20, and the p-type semiconductor layer of the light emitting element 150may be connected to the first pixel power ELVDD via the transistor part,and the n-type semiconductor layer may be connected to a second pixelpower ELVSS. The first pixel power ELVDD and the second pixel powerELVSS may have different potentials from each other. For example, thesecond pixel power ELVSS may have potential lower than that of the firstpixel power ELVDD, by at least the threshold voltage of the lightemitting element 150. Each of these light emitting elements 150 emitslight with a luminance corresponding to the driving current controlledby the transistor part.

According to an exemplary embodiment, the transistor part includes firstand a second transistors M1 and M2 and a storage capacitor Cst. However,the inventive concepts are not limited, and the circuit configuration ofa pixel may be variously modified.

The source electrode of the first transistor M1 (e.g., switchingtransistor) is connected to the data line 120, and the drain electrodeis connected to the first node Ni. Further, the gate electrode of thefirst transistor M1 is connected to the first scan line 130 _(R). Thefirst transistor M1 may be turned on when a scan signal having a voltagecapable of turning on the first transistor M1 is supplied from the firstscan line 130 _(R) to the data line 120, to electrically connect thefirst node Ni. For example, the data signal of the corresponding frameis supplied to the data line 120, and accordingly, the data signal istransmitted to the first node Ni. The data signal transmitted to thefirst node Ni is charged in the storage capacitor Cst.

The source electrode of the second transistor M2 is connected to thefirst pixel power ELVDD and the drain electrode is connected to then-type semiconductor layer of the light emitting element 150. The gateelectrode of the second transistor M2 is connected to the first node Ni.The second transistor M2 controls an amount of driving current suppliedto the light emitting element 150 to correspond to the voltage of thefirst node N1.

One electrode of the storage capacitor Cst is connected to the firstpixel power ELVDD, and the other electrode is connected to the firstnode Ni. The storage capacitor Cst charges the voltage corresponding tothe data signal supplied to the first node N1 and maintains the chargedvoltage until the data signal of the next frame is supplied.

FIG. 8 shows a transistor part including two transistors, however, theinventive concepts are not limited thereto, and various modificationsmay be applicable to the structure of the transistor part. For example,the transistor part may include more transistors, capacitors, or thelike each having various structures.

The pixels may be implemented in various structures within the scope ofthe inventive concepts. Hereinafter, a pixel will be described as havinga passive matrix type pixel.

FIG. 9 is a plan view of a pixel according to an exemplary embodiment,and FIGS. 10A and 10B are cross-sectional views taken along lines I-I′and II-II′ of FIG. 9, respectively.

Referring to FIGS. 9, 10A and 10B, a pixel according to an exemplaryembodiment a light emitting region in which a plurality of epitaxialstacks are stacked, and a peripheral region surrounding the lightemitting region. The plurality of epitaxial stacks may include first tothird epitaxial stacks 20, 30, and 40.

The pixel according to an exemplary embodiment has a light emittingregion in which a plurality of epitaxial stacks are stacked. At leastone side of the light emitting region is provided with a contact forconnecting the wiring part to the first to third epitaxial stacks 20,30, and 40. The contact includes first and second common contacts 50GCand 50BC for applying a common voltage to the first to third epitaxialstacks 20, 30, and 40, a first contact 20C for providing a lightemitting signal to the first epitaxial stack 20, a second contact 30Cfor providing a light emitting signal to the second epitaxial stack 30,and a third contact 40C for providing a light emitting signal to thethird epitaxial stack 40.

In an exemplary embodiment, the stacked structure may vary depending onthe polarity of the semiconductor layers of the first to third epitaxialstacks 20, 30 m and 40 to which the common voltage is applied.Hereinafter, the stacked structure will be described as being appliedwith a common voltage to a p-type semiconductor layer. In particular,the first to third common contact electrodes will be described ascorresponding to the first to third p-type contact electrodes,respectively.

In an exemplary embodiment, the first and second common contacts 50GCand 50BC, and the first to third contacts 20C, 30C, and 40C may beprovided at various positions. For example, when the light emittingstacked structure has substantially a square shape, the first and secondcommon contacts 50GC and 50BC, and the first to third contacts 20C, 30C,and 40C may be disposed in regions corresponding to respective dies ofthe square in a plan view. However, the positions of the first andsecond common contacts 50GC and 50BC and the first to third contacts20C, 30C and 40C are not limited thereto, and various modifications areapplicable according to the shape of the light emitting stackedstructure.

The plurality of epitaxial stacks includes first to third epitaxialstacks 20, 30, and 40. The first to third epitaxial stacks 20, 30, and40 are connected with first to third light emitting signal lines forproviding light emitting signals to each of the first to third epitaxialstacks 20, 30, and 40, and common line for providing a common voltage toeach of the first to third epitaxial stacks 20, 30, and 40. The first tothird light emitting signal lines may correspond to the first to thirdscan lines 130 _(R), 130 _(G), and 130 _(B), and the common line maycorrespond to the data line 120. Accordingly, the first to third scanlines 130 _(R), 130 _(G), and 130 _(B) and the data line 120 areconnected to the first to third epitaxial stacks 20, 30, and 40,respectively.

Referring to FIG. 9, the first to third scan lines 130 _(R), 130 _(G),and 130 _(B) may extend in a first direction (e.g., in a horizontaldirection). The data line 120 may extend in a second directionintersecting with the first to third scan lines 130 _(R), 130 _(G), and130 _(B) (e.g., in a vertical direction). However, the extendingdirections of the first to third scan lines 130 _(R), 130 _(G), and 130_(B) and the data line 120 are not limited thereto, and variousmodifications are applicable according to the arrangement of the pixels.

The data line 120 and the first p-type contact electrode 25 p may extendin a second direction intersecting the first direction, whileconcurrently providing a common voltage the p-type semiconductor layerof the first epitaxial stack 20. Accordingly, the data line 120 and thefirst p-type contact electrode 25 p may be substantially the samecomponent. Hereinafter, the first p-type contact electrode 25 p may bereferred to as the data line 120, or vice versa.

An ohmic electrode 25 p′ for ohmic contact between the first p-typecontact electrode 25 p and the first epitaxial stack 20 is provided onthe light emitting region provided with the first p-type contactelectrode 25 p. A plurality of ohmic electrodes 25 p′ may be provided.The ohmic electrode 25 p′ is provided for ohmic contact, and may includea variety of materials. For example, the ohmic electrode 25 p′corresponding to the p-type ohmic electrode 25 p′ may include an Au/Znalloy or an Au/Be alloy. In this case, since the material of the ohmicelectrode 25 p′ has lower reflectivity than Ag, Al, Au, or the like,additional reflective electrodes may be further disposed. As anadditional reflective electrode, Ag, Au, or the like may be used, andTi, Ni, Cr, Ta, or the like may be disposed as a buffer layer foradhesion to adjacent components. In this case, the buffer layer may bethinly deposited on the upper and lower surfaces of the reflectiveelectrode including Ag, Au, or the like.

The first scan line 130 _(R) is connected to the first epitaxial stack20 through the first contact hole CH1, and the data line 120 isconnected via the ohmic electrode 25 p′. The second scan line 130 _(G)is connected to the second epitaxial stack 30 through the second contacthole CH2, and the data line 120 is connected through the 4 a ^(th) and 4b ^(th) contact holes CH4 a and CH4 b. The third scan line 130 _(B) isconnected to the third epitaxial stack 40 through the third contact holeCH3, and the data line 120 is connected through the 5 a ^(th) and 5 b^(th) contact holes CH5 a and CH5 b.

An adhesive layer, a contact electrode, a wavelength pass filter, or thelike are provided between the substrate 10 and the first to thirdepitaxial stacks 20, 30 and 40, respectively. Hereinafter, a pixelaccording to an exemplary embodiment will be described with reference toan order of stacking.

According to the exemplary embodiment, a first epitaxial stack 20 isprovided on the substrate 10 with an adhesive layer 61 interposedtherebetween. The first epitaxial stack 20 may include a p-typesemiconductor layer, an active layer, and an n-type semiconductor layerdisposed in sequence from lower to upper sides.

An insulating film 81 is stacked on a lower surface of the firstepitaxial stack 20 to face the substrate 10. The insulating film 81formed on the lower surface of the first epitaxial stack 20 may includea material that transmits or absorbs light. A plurality of contact holesare formed in the insulating film 81. The contact holes are providedwith an ohmic electrode 25 p′ in contact with the p-type semiconductorlayer of the first epitaxial stack 20. The ohmic electrode 25 p′ mayinclude a variety of materials. The first p-type contact electrode 25 pand the data line 120 are in contact with the ohmic electrode 25 p′. Thefirst p-type contact electrode 25 p (also serving as the data line 120)is provided between the insulating film 81 and the adhesive layer 61.

When viewed from plan view, the first p-type contact electrode 25 p maybe provided in a form such that the first p-type contact electrode 25 poverlaps the first epitaxial stack 20, or more particularly, overlapsthe light emitting region of the first epitaxial stack 20, whilecovering most, or all of the light emitting region. The first p-typecontact electrode 25 p may include a reflective material so that thefirst p-type contact electrode 25 p may reflect light from the firstepitaxial stack 20. The insulating film 81 may also be formed to have areflective property to facilitate the reflection of light from the firstepitaxial stack 20. For example, the insulating film 81 may have anomni-directional reflector (ODR) structure.

The material of the first p-type contact electrode layer 25 p isselected from metals having high reflectivity to light emitted from thefirst epitaxial stack 20, to maximize the reflectivity of light emittedfrom the first epitaxial stack 20. For example, when the first epitaxialstack 20 emits red light, a metal having a high reflectivity to redlight, for example, Au, Al, Ag, or the like may be used as the materialof the first p-type contact electrode layer 25 p. Au does not have ahigh reflectivity to light emitted from the second and third epitaxialstacks 30 and 40 (e.g., green light and blue light), and thus, canreduce a mixture of colors by light emitted from the second and thirdepitaxial stacks 30 and 40.

The first n-type contact electrode 21 n is provided on an upper surfaceof the first epitaxial stack 20. In an exemplary embodiment, the firstn-type contact electrode 21 n may include various metals and metalalloys, including Au/Te alloy or Au/Ge alloy, for example.

The first n-type contact electrode 21 n is provided in a regioncorresponding to the first contact 20C and may include a conductivematerial.

The second adhesive layer 63 is provided on the first epitaxial stack20. The first wavelength path filter 71, the second p-type contactelectrode 35 p, and the second epitaxial stack are sequentially providedon the second adhesive layer 63. The second epitaxial stack 30 mayinclude an n-type semiconductor layer, an active layer, and a p-typesemiconductor layer sequentially disposed from lower to upper sides.

The first wavelength pass filter 71 is provided on the upper surface ofthe first epitaxial stack 20 to cover substantially all the lightemitting region of the first epitaxial stack 20.

In an exemplary embodiment, the region corresponding to the firstcontact 20C of the second epitaxial stack 30 is removed, therebyexposing a portion of the upper surface of the first n-type contactelectrode 21 n. In addition, the second epitaxial stack 30 may have asmaller area than the second p-type contact electrode 35 p. The regioncorresponding to the first common contact 50GC is removed from thesecond epitaxial stack 30, thereby exposing a portion of the uppersurface of the second p-type contact electrode 35 p.

The third adhesive layer 65 is provided on the second epitaxial stack30. The second wavelength path filter 73 and the third p-type contactelectrode 45 p are sequentially provided on the third adhesive layer 65.The third epitaxial stack 40 is provided on the third p-type contactelectrode 45 p. The third epitaxial stack 40 may include a p-typesemiconductor layer, an active layer, and an n-type semiconductor layersequentially stacked from lower to upper sides.

The third epitaxial stack 40 may have a smaller area than the secondepitaxial stack 30. The third epitaxial stack 40 may have a smaller areathan the third p-type contact electrode 45 p. The region correspondingto the second common contact 50BC is removed from the third epitaxialstack 40, thereby exposing a portion of the upper surface of the thirdp-type contact electrode 45 p.

The first optically non-transmissive film 83 covering the stackedstructure of the first to third epitaxial stacks 20, 30, and 40 isprovided on portions of the sides and the upper surfaces of the first tothird epitaxial stacks 20, 30, and 40. The first opticallynon-transmissive film 83 may include various organic/inorganicinsulating materials, and is not limited thereto. For example, the firstoptically non-transmissive film 83 may be a DBR or an organic polymerfilm having a black color. In an exemplary embodiment, a floating metalreflective film may further be provided on the first opticallynon-transmissive film 83. In an exemplary embodiment, the opticallynon-transmissive film may be formed by depositing two or more insulatingfilms having refractive indices different from each other.

The first contact hole CH1 is formed in the first opticallynon-transmissive film 83 to expose an upper surface of the first n-typecontact electrode 21 n provided in the first contact 20C.

A first scan line 130 _(R) is provided on the first opticallynon-transmissive film 83. The first scan line 130 _(R) is connected tothe first n-type contact electrode 21 n through the first contact holeCH1.

A second optically non-transmissive film 85 is provided on the firstoptically non-transmissive film 83. The second opticallynon-transmissive film 85 is also provided on portions of the sides andthe upper surfaces of the first to third epitaxial stacks 20, 30, and40, covering the stacked structure of the first to third epitaxialstacks 20, 30, and 40. The second optically non-transmissive film 85 mayinclude substantially the same or different materials from the firstoptically non-transmissive film 83. The second opticallynon-transmissive film 85 may also be a DBR or an organic polymer filmhaving a black color. In an exemplary embodiment, a floating metalreflective film may further be provided on the second opticallynon-transmissive film 85. In an exemplary embodiment, the opticallynon-transmissive film may be formed by depositing two or more insulatingfilms having different refractive indices from each other.

The second and third scan lines 130 _(G) and 130 _(B) and the first andsecond bridge electrodes BR_(G) and BR_(B) are provided on the secondoptically non-transmissive film 85. The second opticallynon-transmissive film 85 is provided with a second contact hole CH2 forexposing an upper surface of the second epitaxial stack 30 at the secondcontact 30C, that is, exposing the n-type semiconductor layer of thesecond epitaxial stack 30, a third contact hole CH3 for exposing anupper surface of the third epitaxial stack 40 at the third contact 40C,that is, exposing an n-type semiconductor layer of the third epitaxialstack 40, 4 a ^(th) and 4 b ^(th) contact holes CH4 a and CH4 b forexposing an upper surface of the first p-type contact electrode 25 p andan upper surface of the second p-type contact electrode 35 p, at thefirst common contact 50GC, and 5 a ^(th) and 5 b ^(th) contact holes CH5a and CH5 b for exposing an upper surface of the first p-type contactelectrode 25 p and an upper surface of the third p-type contactelectrode 45 p, at the second common contact 50BC.

The second scan line 130 _(G) is connected to the n-type semiconductorlayer of the second epitaxial stack 30 through the second contact holeCH2. The third scan line 130 _(B) is connected to the n-typesemiconductor layer of the third epitaxial stack 40 through the thirdcontact hole CH3. The data line 120 is connected to the second p-typecontact electrode 35 p through the 4 a ^(th) and 4 b ^(th) contact holesCH4 a and CH4 b and the first bridge electrode BR_(G). The data line 120is also connected to the third p-type contact electrode 45 p through the5 a ^(th) and 5 b ^(th) contact holes CH5 a and CH5 b and the secondbridge electrode BR_(B).

FIGS. 9 to 10B show that the second and third scan lines 130 _(G) and130 _(B) are electrically connected to the n-type semiconductor layer ofthe second and third epitaxial stacks and 40 in direct contact with eachother. However, the inventive concepts are not limited thereto, thesecond and third n-type contact electrodes may be further providedbetween the second and third scan lines 130 _(G) and 130 _(B) and then-type semiconductor layers of the second and third epitaxial stacks 30and 40.

Irregularities may be selectively provided on the upper surfaces of thefirst to third epitaxial stacks 20, 30, and 40, that is, on the uppersurfaces of the first to third epitaxial stacks 20, 30, and 40. Each ofthe irregularities may be provided only at a portion corresponding tothe light emitting region, or may be provided over substantially theentire upper surface of the respective semiconductor layers.

In an exemplary embodiment, the first and second opticallynon-transmissive films 83 and 85 may completely cover the sides of thefirst to third epitaxial stacks 20, 30, and 40. The first and secondoptically non-transmissive films 83 and 85 may cover a portion of theupper surface of the third epitaxial stack 40. Accordingly, the firstand second optically non-transmissive films 83 and 85 are not providedin the light emitting region so that light emitted from the first tothird epitaxial stacks may travel in upper direction.

In addition, in an exemplary embodiment, a metal-based additionaloptically non-transmissive film may be further provided on the sides ofthe first and/or second optically non-transmissive films 83 and 85 thatcorrespond to the sides of the pixels. The additional opticallynon-transmissive film is an additional light blocking film that includesa light absorbing or reflective material, which is provided to preventthe light from the first to third epitaxial stacks 20, 30, and 40 fromemerging through the sides of the pixels.

In an exemplary embodiment, the additional optically non-transmissivefilm may be formed as a single or multi-layered metal. For example, theadditional optically non-transmissive film may be formed of a variety ofmaterials including metals such as Al, Ti, Cr, Ni, Au, Ag, Ti, Sn, Ni,Cr, W, Cu, or others, or alloys thereof. The additional opticallynon-transmissive film may be provided on the sides of the first and/orsecond insulating films 83 and 85 as a separate layer formed of amaterial, such as metal or alloy thereof.

The additional optically non-transmissive film may be formed separatelyfrom the first to third scan lines 130 _(R), 130 _(G), and 130 _(B) andthe first and second bridge electrodes BR_(G) and BR_(B), on the samelayer and using substantially the same material during the same processof forming at least one of the first to third scan lines 130 _(R), 130_(G), and 130 _(B) and the first and second bridge electrodes BR_(G) andBR_(B). In this case, the optically non-transmissive film may beelectrically insulated from the first to third scan lines 130 _(R), 130_(G), and 130 _(B) and the first and second bridge electrodes BR_(G) andBR_(B).

In an exemplary embodiment, the additional optically non-transmissivefilm may be provided in such a form that is laterally extending from atleast one of the first to third scan lines 130 _(R), 130 _(G) and 130_(B) and the first and second bridge electrodes BR_(G) and BR_(B). Inthis case, the optically non-transmissive film extending from one of thefirst to third scan lines 130 _(R), 130 _(G), and 130 _(B) and the firstand second bridge electrodes BR_(G) and BR_(B) may not be electricallyconnected to other conductive components.

The pixel having the structure described above may be manufactured bystacking the first to third epitaxial stacks 20, 30, and 40 on thesubstrate 10 sequentially and patterning the same, which will bedescribed in detail below with reference to the drawings.

FIGS. 11 to 21 are plan views sequentially showing a method ofmanufacturing a pixel on a substrate. FIGS. 12A and 12B to 22A and 22Bare cross-sectional views taken along line I-I′ and line II-II′ ofcorresponding figures, such as FIGS. 11 and 21, respectively.

Referring to FIGS. 11, 12A and 12B, the first to third epitaxial stacks20, 30, and are sequentially formed on the substrate 10, and the thirdepitaxial stack 40 is patterned.

In order to sequentially form the first to third epitaxial stacks 20,30, and 40 on the substrate 10, the first epitaxial stack 20 and theohmic electrode 25 p′ are formed on a first temporary substrate. In anexemplary embodiment, the first temporary substrate may be asemiconductor substrate, such as a GaAs substrate for forming the firstepitaxial stack 20. The first epitaxial stack 20 is fabricated bystacking the n-type semiconductor layer, the active layer, and thep-type semiconductor layer on the first temporary substrate. Theinsulating film 81 having a contact hole is formed on the firsttemporary substrate, and the ohmic electrode 25 p′ is formed within thecontact hole of the insulating film 81.

The ohmic electrode 25 p′ is formed by forming the insulating film 81 onthe first temporary substrate, applying photoresist, patterning thephotoresist, depositing an ohmic electrode 25 p′ material on thepatterned photoresist, and then lifting off the photoresist pattern.However, the method of forming the ohmic electrode 25 p′ is not limitedthereto. For example, the insulating film 81 may be formed by formingthe insulating film 81, patterning the insulating film 81 byphotolithography, forming the ohmic electrode film 25 p′ with the ohmicelectrode film 25 p′ material, and then patterning the ohmic electrodefilm 25 p′ by photolithography.

The first p-type contact electrode layer 25 p (also serving as the dataline 120) is formed on the first temporary substrate on which the ohmicelectrode 25 p′ is formed. The first p-type contact electrode layer 25 pmay include a reflective material. The first p-type contact electrodelayer 25 p may be formed by, for example, depositing a metallic materialand then patterning the same using photolithography.

The first epitaxial stack 20 formed on the first temporary substrate isinverted and attached to the substrate 10 via the first adhesive layer61 interposed therebetween.

After the first epitaxial stack 20 is deposited on the substrate 10, thefirst temporary substrate is removed. The first temporary substrate maybe removed by various methods such as wet etching, dry etching, physicalremoval, laser lift-off, or the like.

After the removal of the first temporary substrate, the first n-typecontact electrode 21 n is provided on an upper surface of the firstepitaxial stack 20. The first n-type contact electrode 21 n may beformed by depositing a conductive material and then patterning by thephotolithography process.

After removing the first temporary substrate, irregularities may beformed on an upper surface (n-type semiconductor layer) of the firstepitaxial stack 20. The irregularities may be formed by texturing withvarious etching processes. For example, the irregularities may be formedby various methods such as dry etching using a micro photo process, wetetching using a crystal characteristic, texturing using a physicalmethod, such as sand blasting, ion beam etching, texturing based ondifference in etching rates of block copolymers, or the like.

The second epitaxial stack 30, the second p-type contact electrode layer35 p, and the first wavelength pass filter 71 are formed on a separatesecond temporary substrate.

The second temporary substrate may be a sapphire substrate. The secondepitaxial stack 30 may be fabricated by forming the n-type semiconductorlayer, the active layer, and the p-type semiconductor layer on thesecond temporary substrate.

The second epitaxial stack 30 formed on the second temporary substrateis inverted and attached to the first epitaxial stack 20 via the secondadhesive layer 63 interposed therebetween.

After the attachment, the second temporary substrate is removed. Thesecond temporary substrate may be removed by various methods such as wetetching, dry etching, physical removal, laser lift-off, or the like.

After removing the second temporary substrate, irregularities may beformed on an upper surface (n-type semiconductor layer) of the secondepitaxial stack 30. The irregularities may be textured through variousetching processes, or may be formed by using a patterned sapphiresubstrate for the second temporary substrate.

The third epitaxial stack 40, the third p-type contact electrode layer45 p, and the second wavelength pass filter 73 are formed on a separatethird temporary substrate.

The third temporary substrate may be a sapphire substrate. The thirdepitaxial stack 40 may be fabricated by forming the n-type semiconductorlayer, the active layer, and the p-type semiconductor layer on the thirdtemporary substrate.

The third epitaxial stack 40 formed on the third temporary substrate isinverted to and attached to the second epitaxial stack 30 via the thirdadhesive layer 65 interposed therebetween.

After attachment, the third temporary substrate is removed. The thirdtemporary substrate may be removed by various methods such as wetetching, dry etching, physical removal, laser lift-off, or the like.After the third temporary substrate is removed, irregularities may beformed on an upper surface (n-type semiconductor layer) of the thirdepitaxial stack 40. The irregularities may be textured through variousetching processes, or may be formed by using a patterned sapphiresubstrate for the third temporary substrate.

Next, the third epitaxial stack 40 is patterned. Portions of the thirdepitaxial stack except for the light emitting region are removed. Inparticular, the portions corresponding to the first and second contacts20C and 30C and the first and second common contacts 50GC and 50BC areremoved. As such, a portion of the upper surface of the third p-typecontact electrode 45 p is exposed to the outside at the second commoncontact 50BC. The third epitaxial stack 40 may be removed by variousmethods, such as wet etching or dry etching using photolithography, andthe third p-type contact electrode 45 p may function as an etch stopper.

According to an exemplary embodiment, the side of the third epitaxialstack 40 is obliquely patterned with respect to one side of thesubstrate 10, and the angle formed between the third epitaxial stack 40and one side of the substrate 10 may be between about 45 degrees andabout 85 degrees.

The third p-type contact electrode 45 p, the second wavelength passfilter 73, and the third adhesive layer 65 are then patterned. As such,a portion of the upper surface of the second epitaxial stack 30 isexposed.

The third p-type contact electrode 45 p, the second pass filter 73, andthe third adhesive layer 65 may be removed by various methods such aswet etching or dry etching using photolithography.

Referring to FIGS. 13, 14A and 14B, a portion of the second epitaxialstack 30 is removed, exposing a portion of the upper surface of thesecond p-type contact electrode 35 p at the second common contact 50GCto the outside. The third p-type contact electrode 45 p may function asan etch stopper during etching.

The side of the second epitaxial stack 30 is obliquely patterned withrespect to one side of the substrate 10, and the angle formed betweenthe second epitaxial stack 30 and one side of the substrate 10 may bebetween about 45 degrees and about 85 degrees.

Next, portions of the second p-type contact electrode 35 p, the firstwavelength pass filter 71, and the second adhesive layer 63 are etched.Accordingly, the upper surface of the first n-type contact electrode 21n is exposed at the first contact 20C, and the upper surface of thefirst epitaxial stack 20 is exposed at the portions other than the lightemitting region.

The second epitaxial stack 30, the second p-type contact electrode 35 p,the first wavelength pass filter 71, and the second adhesive layer 63may be removed by various methods such as wet etching or dry etchingusing photolithography.

Referring to FIGS. 15, 16A and 16B, the first epitaxial stack 20 and theinsulating film 81 are removed from the region excluding the lightemitting region. The upper surface of the first p-type contact electrode25 p is exposed at the first and second common contacts 50GC and 50BC.

The side of the first epitaxial stack 20 is obliquely patterned withrespect to one side of the substrate 10, and the angle formed betweenthe first epitaxial stack 20 and one side of the substrate 10 may bebetween about 45 degrees and about 85 degrees.

The angles formed by the first to third epitaxial stacks 20, 30 and 40with respect to one surface of the substrate may be substantially thesame or different from each other, although substantially the sameangles are illustrated in the drawing for convenience of explanation.The components excluding the first to third epitaxial stacks 20, 30, and40, e.g., the first and second p-type contact electrodes 25 p and 35 p,the first and second adhesive layers 61 and 63, and the first and secondwavelength pass filters 71 and 73 may be obliquely patterned to have apredetermined angle with respect to one side of the substrate. Accordingto another exemplary embodiment, the angles formed by the first andsecond p-type contact electrodes 25 p and 35 p, the first and secondadhesive layers 61 and 63, the first and second wavelength pass filters71 and 73 with respect to one side of the substrate are not limitedthereto, and accordingly, the angles may be varied depending on thecomponents being etched together in the same process, or may haveindividually different angles from each other, as long as the angleformed between each of the components and one side of the substrate maybe between about 45 degrees and about 85 degrees.

Referring to FIGS. 17, 18A and 18B, the first optically non-transmissivefilm 83 is formed on a front side of the substrate 10. Next, uponremoval of the first optically non-transmissive film 83 from the uppersurface of the substrate 10 that corresponds to the light emittingregion, the first to third contact holes CH1, CH2, and CH3, the 4 a^(th) and 4 b ^(th) contact holes CH4 a and CH4 b, and the 5 a ^(th) and5 b ^(th) contact holes CH5 a and CH5 b are formed.

After deposition, the first optically non-transmissive film 83 may bepatterned by various methods such as wet etching or dry etching usingphotolithography.

Referring to FIGS. 19, 20A and 20B, the first scan line 130 _(R) isformed on the patterned first optically non-transmissive film 83. Thefirst scan line 130 _(R) is connected to the first n-type contactelectrode 21 n through the first contact hole CH1 at the first contact20C. The first scan line 130 _(R) may be formed in various ways. Forexample, the first scan line 130 _(R) may be formed by photolithography.

Next, the second optically non-transmissive film 85 is formed on thefront side of the substrate 10. Next, preferably simultaneously withremoval of the first optically non-transmissive film 83 from the uppersurface of the substrate 10 that corresponds to the light emittingregion, the second and third contact holes CH2 and CH3, the 4 a ^(th)and 4 b ^(th) contact holes CH4 a and CH4 b, and the 5 a ^(th) and 5 b^(th) contact holes CH5 a and CH5 b are formed. After deposition, thesecond optically non-transmissive film 85 may be patterned by variousmethods such as wet etching or dry etching using photolithography.

Referring to FIGS. 21, 22A and 22B, the second scan line 130 _(G), thethird scan line 130 _(B), the first bridge electrode BR_(G), and thesecond bridge electrode BR_(B) are formed on the patterned secondoptically non-transmissive film 85.

The second scan line 130 _(G) is connected to the n-type semiconductorlayer of the second epitaxial stack 30 through the second contact holeCH2 at the second contact 30C. The third scan line 130 _(B) is connectedto the n-type semiconductor layer of the third epitaxial stack 40through a third contact hole CH3 at the third contact 40C. The firstbridge electrode BR_(G) is connected to the first p-type contactelectrode 25 p through the 4 a ^(th) and 4 b ^(th) contact holes CH4 aand CH4 b at the fourth common contact 50GC. The second bridge electrodeBR_(B) is connected to the first p-type contact electrode 25 p throughthe 5 a ^(th) and 5 b ^(th) contact holes CH5 a and CH5 b at the secondcommon contact 50BC.

The second scan line 130 _(G), the third scan line 130 _(B), and thebridge electrode 120 b may be formed on the second non-transmissive film85 in various ways, for example, by photolithography.

The second scan line 130 _(G), the third scan line 130 _(B), and thefirst and second bridge electrodes BR_(G) and BR_(B) may be formed byapplying photoresist on the substrate 10 on which the second opticallynon-transmissive film 85 is formed, and then patterning the photoresist,and depositing materials of the second scan line 130 _(G), the thirdscan line 130 _(B), and the bridge electrode on the patternedphotoresist and then lifting off the photoresist pattern.

According to an exemplary embodiment, the order of forming the first tothird scan lines 130 _(R), 130 _(G), and 130 _(B) and the first andsecond bridge electrodes BR_(G) and BR_(B) of the wiring part is notparticularly limited, and may be formed in different sequences. Moreparticularly, the second scan line 130 _(G), the third scan line 130_(B), and the first and second bridge electrodes BR_(G) and BR_(B) aredescribed as being formed on the second optically non-transmissive film85 during the same stage, but they may be formed in a different order.For example, the first scan line 130 _(R) and the second scan line 130_(G) may be first formed in the same step, followed by the formation ofthe additional insulating film and then the third scan line 130 _(B).Alternatively, the first scan line 130 _(R) and the third scan line 130_(B) may be formed first in the same step, followed by the formation ofthe additional insulating film, and then the formation of the secondscan line 130 _(G). In addition, the first and second bridge electrodesBR_(G) and BR_(B) may be formed together at any of the steps of formingthe first to third scan lines 130 _(R), 130 _(G), and 130 _(B).

In addition, in an exemplary embodiment, the positions of the contactsof the respective epitaxial stacks 20, 30, and 40 may be formeddifferently, in which case the positions of the first to third scanlines 130 _(R), 130 _(G), and 130 _(B) and the first and second bridgeelectrodes BR_(G) and BR_(B) may also be changed.

In an exemplary embodiment, an additional optically non-transmissivefilm may be further provided on the first optically non-transmissivefilm 83 or the second optically non-transmissive film 85, on a portionthat corresponds to the side of the pixel.

As described above, in a display device according to an exemplaryembodiment, it is possible to sequentially stack a plurality ofepitaxial stacks and then form contacts with a wiring part at aplurality of epitaxial stacks at the same time.

A light emitting stacked structure according to an exemplary embodimentmay be modified into various forms. In the following exemplaryembodiments, differences from the light emitting stacked structuredescribed above will be mainly described to avoid redundancy.

FIG. 23 is a cross-sectional view of a light emitting stacked structureaccording to an exemplary embodiment.

Referring to FIG. 23, a light emitting stacked structure according to anexemplary embodiment includes a plurality of sequentially stackedepitaxial stacks, and optically non-transmissive films covering sides ofthe epitaxial stacks, and a plurality of epitaxial stacks disposedsequentially on the upper surface of the substrate 10.

A plurality of epitaxial stacks are stacked on the upper surface of thesubstrate 10 in the order of the third epitaxial stack 40, the secondepitaxial stack 30, and the first epitaxial stack 20.

The substrate 10 may be formed of an optically transmissive insulatingmaterial. As used herein, the substrate 10 being “opticallytransmissive” not only refers to a transparent substrate that transmitsthe entire light, but also a semi-transparent or partially transparentsubstrate that transmits only a light of a predetermined wavelength, ortransmits only a portion of a light of a predetermined wavelength, orthe like.

The substrate 10 may be allow the third epitaxial stack 40 to be grownthereon. For example, the substrate 10 may be a sapphire substrate.However, the inventive concepts are not limited to a particular type ofthe substrate 10, and may be any type of a substrate as long asepitaxial stack may be grown thereon and has optically transmissive andinsulating properties. Examples of the material of the substrate 10include glass, quartz, organic polymer, organic/inorganic composite, andso on. In an exemplary embodiment, the substrate 10 may further includea wiring part that may provide a light emitting signal and a commonvoltage to the respective epitaxial stacks. As such, the substrate 10may be provided as a printed circuit board or as a composite substratehaving a wiring part and/or a drive element formed on glass, silicon,quartz, organic polymer, or organic/inorganic composite.

Each of the epitaxial stacks emits light to the back direction of thesubstrate 10, as shown in FIG. 23. Light emitted from one epitaxialstack is passed through another epitaxial stack located in the lightpath, and travels to the back direction. In this case, the backdirection corresponds to a direction along which the first to thirdepitaxial stacks 20, 30 and 40 are stacked.

In the exemplary embodiment, the first epitaxial stack 20 may emit afirst color light L1, the second epitaxial stack 30 may emit a secondcolor light L2, and the third epitaxial stack 40 may emit the thirdcolor light L3. The first to third color light L1, L2, and L3 correspondto different color light from each other, and the first to third colorlight L1, L2, and L3 may be color light of different wavelength bandsfrom each other, which have sequentially decreasing wavelengths. Inparticular, the first to third color light L1, L2, and L3 may havedifferent wavelength bands from each other, and the color light may be ashorter wavelength band of a higher energy in the order of the firstcolor light L1 to the third color light L3. In the exemplary embodiment,the first color light L1 may be red light, the second color light L2 maybe green light, and the third color light L3 may be blue light. However,the inventive concepts are not limited to a particular color of lightemitted from each epitaxial stack, and the epitaxial stacks may emitdifferent colors of light.

An optically non-transmissive film 80 is provided on the sides of thefirst to third epitaxial stacks 20, 30, and 40. The opticallynon-transmissive film 80 may substantially completely covers the sidesof the first to third epitaxial stacks 20, 30, and 40. Also, in anexemplary embodiment, the optically non-transmissive film 80 covers thesides of the epitaxial stacks as well as the upper surface of theuppermost epitaxial stack positioned on top of the rest epitaxialstacks. In particular, the optically non-transmissive film 80 overlapsthe epitaxial stacks in plan view. Accordingly, among light emitted fromthe respective epitaxial stacks, light directed in an upper direction isreflected from or absorbed by the optically non-transmissive film 80,and in particular, when light is reflected by the opticallynon-transmissive film 80, the reflected light travels to the backdirection, resulting in enhanced efficiency of the light emission to theback direction. The optically non-transmissive film 80 is notparticularly limited as long as it blocks a transmission of light byabsorbing or reflecting light.

In an exemplary embodiment, the side of each of the epitaxial stacks hasan inclined shape relative to one side of the substrate 10. According toan exemplary embodiment, an angle between the sides of the first tothird epitaxial stacks 20, 30, and 40 and one side of the substrate 10is greater than about 0 degrees and less than about 90 degrees. Forexample, when the angles between the sides of the first to thirdepitaxial stacks 20, 30, and 40 and one side of the substrate is firstto third angles θ₁, θ₂, and θ₃, the first to third angles θ₁, θ₂, and θ₃may have values in a range from about 45 degrees to about 85 degrees,respectively.

When the sides of the first to third epitaxial stacks 20, 30 and 40 havea predetermined inclination, the optically non-transmissive film 80 maybe easily formed. Further, in an exemplary embodiment, each of theepitaxial stacks has a tapered shape at a predetermined angle, which canmaximize the light reflection effect by the optically non-transmissivefilm 80. In particular, according to an exemplary embodiment, it ispossible to easily adjust the angles of the sides of the first to thirdepitaxial stacks 20, 30, and 40, to enhance the extraction efficiency oflight emitted from the first to third epitaxial stacks 20, 30, and 40.

In an exemplary embodiment, the angles between the sides of each of thefirst to third epitaxial stacks 20, 30, and 40 and one side of thesubstrate 10 may be substantially the same or different from each other.For example, among the angles formed between the sides of the first tothird epitaxial stacks 20, 30, and 40 and one side of the substrate 10,the first angle θ₁, the second angle θ₂, and the third angle θ₃ may allbe different from one another, or alternatively, the second angle θ₂ andthe third angle θ₃ may be substantially the same as each other anddifferent from the first angle θ₁.

In the light emitting stacked structure according to an exemplaryembodiment, the signal lines for applying emitting signals to therespective epitaxial stacks are independently connected, andaccordingly, the respective epitaxial stacks can be independentlydriven, and thus, the light emitting stacked structure can implementvarious colors according to whether light is emitted from each of theepitaxial stacks. In addition, the epitaxial stacks for emitting thelight of different wavelengths from each other are overlapped verticallyon one another, and thus, can be formed in a narrow area. In addition,since the sides of the epitaxial stacks are inclined, it is possible toeasily form the non-transmissive film with a sufficient thickness, andthe non-transmittance film can prevent the phenomenon in which lightemitted from a certain pixel affects the adjacent pixels, or in whichcolor is mixed with the light emitted from the adjacent pixels.

FIG. 24 is a cross-sectional view of a light emitting stacked structureincluding a wiring part according to an exemplary embodiment. In FIG.24, the inclined shapes of each of the epitaxial stacks and theinsulating films shown in FIG. 23 are omitted.

Referring to FIG. 24, in the light emitting stacked structure accordingto an exemplary embodiment, the third epitaxial stack 40 may be providedon the substrate 10, and the second adhesive layer 63 may be provided onthe third epitaxial stack 40 via the second epitaxial stack 30interposed therebetween, and the first epitaxial stack 20 may beprovided on the second epitaxial stack 30 via the first adhesive layer61 interposed therebetween.

The first and second adhesive layers 61 and 63 may include anon-conductive material and an optically transmissive material. Forexample, an optically clear adhesive may be used for the first andsecond adhesive layers 61 and 63. The material for forming the first andsecond adhesive layers 61 and 63 is not particularly limited, as long asit is optically transparent and capable of attaching each of theepitaxial stacks stably.

The third epitaxial stack 40 includes the n-type semiconductor layer 41,the active layer 43, and the p-type semiconductor layer 45, which aresequentially disposed from lower to upper sides. The n-typesemiconductor layer 41, the active layer 43, and the p-typesemiconductor layer 45 of the third epitaxial stack 40 may include asemiconductor material that emits blue light. However, the inventiveconcepts are not limited thereto, and the third epitaxial stack 40 mayemit color of light other than blue. A third p-type contact electrode 45p is provided above the p-type semiconductor layer 45 of the thirdepitaxial stack 40.

The second epitaxial stack 30 includes the p-type semiconductor layer35, the active layer 33, and the n-type semiconductor layer 31, whichare sequentially disposed from lower to upper sides. The p-typesemiconductor layer 35, the active layer 33, and the n-typesemiconductor layer 31 of the second epitaxial stack 30 may include asemiconductor material that emits green light. However, the inventiveconcepts are not limited thereto, and the second epitaxial stack 30 mayemit color of light other than green. A second p-type contact electrode35 p is provided under the p-type semiconductor layer 35 of the secondepitaxial stack 30.

The first epitaxial stack 20 includes the n-type semiconductor layer 21,the active layer 23, and the p-type semiconductor layer 25, which aresequentially disposed from lower to upper sides. The n-typesemiconductor layer 21, the active layer 23, and the p-typesemiconductor layer 25 of the first epitaxial stack 20 may include asemiconductor material that emits red light. However, the inventiveconcepts are not limited thereto, and the first epitaxial stack 20 mayemit color of light other than red. A first p-type contact electrode 25p is provided above the p-type semiconductor layer 25 of the firstepitaxial stack 20.

In an exemplary embodiment, common lines may be connected to the thirdp-type contact electrodes 45 p, the second p-type contact electrode 35p, and the first p-type contact electrodes 25 p. The common line may bea line to which the common voltage is applied. In addition, the lightemitting signal lines may be connected to the n-type semiconductorlayers 21, 31, and 41 of the first to third epitaxial stacks 20, 30, and40, respectively. In the exemplary embodiment, a common voltage Sc isapplied to the first to third p-type contact electrodes 25 p, 35 p, and45 p through the common line, and the light emitting signal is appliedto the n-type semiconductor layers 21, 31, and 41 of the first to thirdepitaxial stacks 20, 30, and 40 through the light emitting signal lines,thereby controlling the light emission of the first to third epitaxialstacks 20, 30, and 40. In this case, the light emitting signal includesfirst to third light emitting signals S_(R), S_(G), and S_(B)corresponding to the first to third epitaxial stacks 20, 30, and 40,respectively. In an exemplary embodiment, the first light emittingsignal S_(R) may be a signal corresponding to red light, the secondlight emitting signal S_(G) may be a signal corresponding to greenlight, and the third light emitting signal S_(B) may be a signalcorresponding to an emission of blue light.

According to the exemplary embodiment, the first to third epitaxialstacks 20, 30, and 40 are driven according to a light emitting signalapplied to each of the epitaxial stacks.

In the exemplary embodiment described above, a common voltage isdescribed as being applied to the p-type semiconductor layers 25, 35,and 45 of the first to third epitaxial stacks 20, 30 and 40, and thelight emitting signal is described as being applied to the n-typesemiconductor layers 21, 31, and 41 of the first to third epitaxialstacks 20, 30, and 40, however, the inventive concepts are not limitedthereto.

The light emitting stacked structure according to an exemplaryembodiment may be capable of implementing a color such that portions ofdifferent color light are provided on the overlapped region, rather thanimplementing different color light on different planes spaced apart fromeach other. Accordingly, the light emitting stacked structure accordingto an exemplary embodiment may advantageously provide compactness andintegration of the light emitting element. In addition, according to anexemplary embodiment, since only one light emitting stacked structure,instead of a plurality of light emitting elements, is mounted to thelight emitting stacked structure, the manufacturing method issignificantly simplified.

The light emitting stacked structure may be a light emitting elementcapable of expressing various colors, and thus, may be employed as apixel in a display device. Hereinafter, a light emitting stackedstructure that can be employed as a pixel in a display device will bedescribed.

FIG. 25 is a plan view of a light emitting stacked structure accordingto an exemplary embodiment, and FIG. 26 is a cross-sectional view takenalong line III-III′ of FIG. 25.

Referring to FIGS. 25 and 26, a light emitting stacked structureaccording to an exemplary embodiment includes a light emitting region inwhich a plurality of epitaxial stacks are stacked, and a peripheralregion surrounding the light emitting region. The plurality of epitaxialstacks includes first to third epitaxial stacks 20, 30, and 40.

At least one side of the light emitting region is provided with acontact for connecting the wiring part to the first to third epitaxialstacks 20, 30, and 40. The contact includes a first common contact 50Cfor applying a common voltage to the first to third epitaxial stacks 20,30, and 40, a first contact 20C for providing a light emitting signal tothe first epitaxial stack 20, a second contact 30C for providing a lightemitting signal to the second epitaxial stack 30, and a third contact40C for providing a light emitting signal to the third epitaxial stack40.

In an exemplary embodiment, when the light emitting stacked structurehas substantially a square shape in a plan view, the common contact 50Cand the first to third contacts 20C, 30C, and 40C may be disposed inregions corresponding to respective corners of the square. However, thepositions of the common contact 50C and the first to third contacts 20C,30C, and 40C are not limited thereto and various modifications areapplicable according to the shape of the light emitting stackedstructure.

The first contact 20C is provided with a first pad 20 p electricallyconnected to the first epitaxial stack 20 through the first n-typecontact electrode 21 n. The second contact 30C is provided with a secondpad 30 p electrically connected to the n-type semiconductor layer of thesecond epitaxial stack 30. The third contact 40C is provided with athird pad 40 p electrically connected to the n-type semiconductor layerof the third epitaxial stack 40.

The common contact 50C is provided with a common pad 50P. The common pad50P is electrically connected to the first to third epitaxial stacks 20,30, and 40 through the first to third p-type contact electrodes 25 p, 35p, and 45 p, respectively.

The common contact 50C is provided with an ohmic electrode 25 p′ at aposition overlapping the first p-type contact electrode 25 p. The ohmicelectrode 25 p′ is provided to electrically connect the p-typesemiconductor layer of the first epitaxial stack 20 and the first p-typecontact electrode 25 p, and may be provided at various positions invarious forms. For example, while the ohmic electrode 25 p′ is providedin the common contact 50C, the inventive concepts are not limitedthereto, and the ohmic electrode 25 p′ may be provided in the lightemitting region.

The ohmic electrode 25 p′ may be have substantially a donut shape. Theohmic electrode 25 p′ is provided for ohmic contact and may includevarious materials. In an exemplary embodiment, the ohmic electrode 25 p′corresponding to the p-type ohmic electrode may include an Au/Zn alloyor an Au/Be alloy. In this case, since the material of the ohmicelectrode 25 p′ is lower in reflectivity than Ag, Al, Au, or the like,additional reflective electrodes may be further disposed. As anadditional reflective electrode, Ag, Au, or the like may be used, andTi, Ni, Cr, Ta, or the like may be disposed as a metal adhesive layerfor adhesion to adjacent components. In this case, the metal adhesivelayer may be thinly deposited on the upper and lower surfaces of thereflective electrode including Ag, Au, or the like.

An adhesive layer, a contact electrode, a wavelength pass filter, or thelike are provided between the substrate 10 and the first to thirdepitaxial stacks 20, 30 and 40, respectively.

Referring to FIG. 26, the third to first epitaxial stacks 40, 30, and 20are sequentially provided on the substrate 10.

The third p-type contact electrode 45 p is provided on the thirdepitaxial stack 40. Specifically, the third p-type contact electrode 45p is provided, which contacts the p-type semiconductor layer of thethird epitaxial stack 40. The third p-type contact electrode 45 p mayinclude a transparent conductive material such as transparent conductiveoxide (TCO), for example.

In an exemplary embodiment, a second wavelength pass filter 73 may beprovided on the third p-type contact electrode 45 p. The secondwavelength pass filter 73 is configured to provide high-purity andhigh-efficiency color light, and may be selectively employed in thelight emitting stacked structure. The second wavelength pass filter 73is configured to block light with a relatively short wavelength fromtraveling toward the epitaxial stack that emits light with a longerwavelength.

In an exemplary embodiment, the second wavelength pass filter 73 maytransmit the second color light emitted from the second epitaxial stacks30, while blocking or reflecting light other than the second colorlight. Accordingly, the second color light emitted from the secondepitaxial stack 30 may travel in a direction from upper to lower sides,while the third color light emitted from the third epitaxial stack 40 isblocked from traveling toward the second epitaxial stack 30 and isreflected or blocked by the second wavelength pass filter 73.

The second epitaxial stack 30 is provided on the third epitaxial stack40 formed with the third p-type contact electrode 45 p, via the secondadhesive layer 63 interposed therebetween.

The second p-type contact electrode 35 p is provided under the secondepitaxial stack 30, that is, between the second epitaxial stack 30 andthe second adhesive layer 63.

The first wavelength pass filter 71 may be provided on the secondepitaxial stack 30. The first wavelength pass filter 71 is configured toblock light with relatively short wavelengths from traveling toward theepitaxial stack that emits light with longer wavelengths, and as will bedescribed below, the first wavelength pass filter 71 may transmit afirst color light emitted from the first epitaxial stack 20, whileblocking or reflecting light other than the first color light.Accordingly, the second color light emitted from the first epitaxialstack 20 may travel in a direction from upper to lower sides, while thesecond color light emitted from the second epitaxial stack 30 is blockedfrom traveling toward the first epitaxial stack 20 and is reflected orblocked by the first wavelength pass filter 71.

The first epitaxial stack 20 is provided on the second epitaxial stack30 formed with the second p-type contact electrode 35 p, via the secondadhesive layer 63 interposed therebetween.

Portions of the n-type semiconductor layer, the active layer, and thep-type semiconductor layer are removed, thereby forming a mesa on thefirst epitaxial stack 20. The non-mesa region where the mesa is notformed is removed when a portion of the semiconductor layer(specifically, portion of the n-type semiconductor layer and activelayer) is removed, which may expose the upper surface of the n-typesemiconductor layer. The mesa region generally overlaps with the lightemitting region, and the non-mesa region may overlap the surroundingregion in general, and particularly overlapping with the contact.

The first n-type contact electrode 21 n is provided on the upper surfaceof the exposed n-type semiconductor layer. The first p-type contactelectrode 25 p is provided above the p-type semiconductor layer that hasthe mesa, via the ohmic electrode 25 p′ and the first opticallynon-transmissive film 83 interposed therebetween.

The first optically non-transmissive film 83 covers the upper surface ofthe first epitaxial stack 20 and has a contact hole in a portionprovided with the ohmic electrode 25 p′. The ohmic electrode 25 p′ isprovided to correspond to the region where the common contact 50C isprovided, and may be provided in various shapes, for example,substantially a donut shape.

The first p-type contact electrode 25 p is provided on the firstoptically non-transmissive film 83. When viewed from plan view, thefirst p-type contact electrode 25 p may be provided in a form such thatthe first p-type contact electrode 25 p overlaps the light emittingregion, while covering the entire light emitting region. The firstp-type contact electrode 25 p may include a reflective material toreflect the light from the first epitaxial stack 20 in a lowerdirection. Various reflective metals may be used as a reflectivematerial for forming the first p-type contact electrode 25 p, such asAg, Al, Au, or the like. If necessary, Ti, Ni, Cr, Ta, or others may bedisposed as an adhesive layer for adhesion with the adjacent components.

According to an exemplary embodiment, the first p-type contact electrode25 p may be selected from a material having high reflectivity in thewavelength band of red light of the first epitaxial stack 20. Forexample, the first p-type contact electrode 25 p may include Au that hashigh reflectivity in the wavelength band of red light, in which case Aucan absorb the blue light leaked from thereunder, thus minimizingunnecessary color interference.

The first optically non-transmissive film 83 may also be formed to havea reflective property to facilitate the reflection of light from thefirst epitaxial stack 20. For example, the first opticallynon-transmissive film 83 may have an omni-directional reflector (ODR)structure.

A second optically non-transmissive film 85 is provided on the firstoptically non-transmissive film 83 where the first p-type contactelectrode 25 p is provided. The second optically non-transmissive film85 covers the upper surface of the first epitaxial stack 20 and thesides of each of the components under the second opticallynon-transmissive film 85. The second optically non-transmissive film 85may include a material that blocks an emission of light by absorbing orreflecting the same, in order to prevent the mixture of light emittedfrom the sides of the first to third epitaxial stacks 20, 30, and 40with light emitted from the adjacent light emitting structures. Thesecond optically non-transmissive film 85 may include substantially thesame or different from the first optically non-transmissive film 83. Thesecond optically non-transmissive film 85 may also be a DBR or anorganic polymer film having a black color. In an exemplary embodiment, afloating metal reflective film may further be provided on the secondoptically non-transmissive film 85. In an exemplary embodiment, theoptically non-transmissive film may be formed by depositing two or moreinsulating films having different refractive indices from each other.

The first to third pads 20P, 30P, and 40P and the common pad 50P areprovided on the second optically non-transmissive film 85. The first tothird pads 20P, 30P, and 40P and the common pad 50P may be connected tothe first to third scan lines and data lines, respectively.

The first to third pads 20P, 30P, and 40P and the common pad 50P may beformed of single-layered or multi-layered metals. For example, the firstto third pads 20P, 30P, and 40P and the common pad 50P may be formed ofvarious materials, such as Al, Ti, Cr, Ni, Au, Ag, Ti, Sn, Ni, Cr, W,Cu, or others, or alloys thereof.

Each of the first to third pads 20P, 30P, and 40P and the common pad 50Pare connected to the respective corresponding components through theholes provided thereunder, such as the first to fourth contact holesCH1, CH2, CH3, and CH4 and a first contact hole CH1′.

The common pad 50P is connected to the first p-type contact electrode 25p through the first contact hole CH1′ and connected to the second andthird p-type contacts 35 p and 45 p through the first contact hole CH1.The first pad 20P is connected to the n-type semiconductor layer of thefirst epitaxial stack 20 through the second contact hole CH2. The secondpad 30P is connected to the n-type semiconductor layer of the secondepitaxial stack 30 through the third contact hole CH3. The third pad 40Pis connected to the n-type semiconductor layer of the second epitaxialstack 30 through the fourth contact hole CH4.

The light emitting stacked structure described above may emit light inthe lower direction by emitting light from the first to third epitaxialstacks 20, 30, and 40. The first to third pads 20P, 30P, and 40P and thecommon pad 50P may each be connected to the first to third scan linesand the data lines, and accordingly, separate driving signals may beapplied to the first to third epitaxial stacks 20, 30, and 40 throughthe first to third pads 20P, 30P, and 40P, and a common voltage may beapplied through the common pad 50P. In this manner, the emission of thelight from the first to third epitaxial stacks 20, 30, and 40 can beindependently controlled.

FIGS. 27, 29, 31, and 33 are plan views illustrating a method ofmanufacturing an epitaxial stack according to an exemplary embodiment,and FIGS. 28, 30A and 30B, 32A and 32B, and 34 are cross-sectional viewstaken along line III-III′ in FIGS. 27, 29, 31 and 33, respectively,according to exemplary embodiments.

Referring to FIGS. 27 and 28, a light emitting stacked structureaccording to an exemplary embodiment has a third epitaxial stack 40formed on the substrate 10. The third p-type contact electrode 45 p andthe second wavelength pass filter 73 are formed on the third epitaxialstack 40.

Next, the second epitaxial stack 30 is formed on a fourth temporarysubstrate. The fourth temporary substrate may be a semiconductorsubstrate on which the second epitaxial stack 30 may be formed thereon.The fourth temporary substrate may be set differently depending on thesemiconductor layer desired to be formed. The second epitaxial stack 30may be fabricated by forming the n-type semiconductor layer, the activelayer, and the p-type semiconductor layer on the fourth temporarysubstrate. The second p-type contact electrode 35 p is formed on anupper surface of the second epitaxial stack 30.

The second epitaxial stack 30 formed on the fourth temporary substrateis inverted and then adhered onto the third epitaxial stack 40 formedwith the second adhesive layer 63, and then the fourth temporarysubstrate is removed. The fourth temporary substrate may be removed byvarious methods, such as wet etching, dry etching, physical removal,laser lift-off, or the like.

Next, the first epitaxial stack 20 is formed on the second epitaxialstack 30. The first epitaxial stack 20 may be formed on a fifthtemporary substrate, and the fifth temporary substrate may be asemiconductor substrate on which the second epitaxial stack 30 may beformed. The fifth temporary substrate may be set differently dependingon the semiconductor layer desired to be formed. The first epitaxialstack 20 is fabricated by forming the n-type semiconductor layer, theactive layer, and the p-type semiconductor layer on the fifth temporarysubstrate.

The first epitaxial stack 20 formed on the fifth temporary substrate isinverted and then adhered onto the second epitaxial stack 30 formed withthe first adhesive layer 61, and then the fifth temporary substrate isremoved. The fifth temporary substrate may be removed by variousmethods, such as wet etching, dry etching, physical removal, laserlift-off, or the like.

Next, the active layer of the first epitaxial stack 20, a portion of thep-type semiconductor layer, and, if necessary, a portion of the n-typesemiconductor layer are removed to form a mesa structure. Forming themesa structure allows the upper surface of the n-type semiconductorlayer of the first epitaxial stack 20 to be exposed.

The first n-type contact electrode 21 n is formed on the exposed uppersurface of the n-type semiconductor layer, and a first opticallynon-transmissive film 83 is formed on the first n-type contact electrode21 n. The contact hole is provided on the first opticallynon-transmissive film 83 to expose a portion of the upper surface of thefirst epitaxial stack 20, and the ohmic electrode 25 p′ is formed in thecontact hole.

In an exemplary embodiment, component such as the mesa structure aredescribed as being form on the first epitaxial stack 20, the firstn-type contact electrode 21 n, ohmic electrode 25 p′, or the like afterthe transfer of the first epitaxial stack 20 onto the second epitaxialstack 30, but the inventive concepts are not limited thereto. Accordingto an exemplary embodiment, the first n-type contact electrode 21 n, theohmic electrode 25 p′, or the like may be first formed on the firstepitaxial stack 20 on the first temporary substrate or by using aseparate additional temporary substrate, and then transferring thepatterned first epitaxial stack 20 onto the second epitaxial stack 30.

Referring to FIGS. 29, 30A and 30B, the first p-type contact electrode25 p is formed on the first epitaxial stack 20 that is formed with thefirst optically non-transmissive film 83, or the like. The first p-typecontact electrode 25 p may include a reflective material and is formedto cover the light emitting region. The first p-type contact electrode25 p may be formed by forming a reflective conductive material on thefront side and then patterning the same using photolithography, or thelike.

After the first p-type contact electrode 25 p is formed, portions of thefirst epitaxial stack 20, the first adhesive layer 61, and the firstwavelength pass filter 71 are removed in the regions corresponding tothe non-light emitting region other than the light emitting region, thecommon contact 50C, the second contact 30C, and the third contact 40C,resulting in formation of the first to fourth contact holes CH1, CH2,CH3, and CH4. As such, the upper surface of the n-type semiconductorlayer of the second epitaxial stack 30 is exposed at the second contact30C.

In this case, the first epitaxial stack 20, the first adhesive layer 61,and the first wavelength pass filter 71 may be patterned by dry etchingor wet etching using photolithography. The sides of the first epitaxialstack 20, the first adhesive layer 61, and the first wavelength passfilter 71 are obliquely patterned with respect to one surface of thesubstrate 10. Specifically, the angle formed between the first epitaxialstack 20 and one side of the substrate may be between about 45 degreesand about 85 degrees.

Referring to FIGS. 31, 32A and 32B, in the first contact hole CH1 of thecommon contact 50C, which is one of the regions corresponding to thenon-light emitting region other than the light emitting region, thecommon contact 50C, the second contact 30C, the third contact 40C, and aportion of the upper surface of the second epitaxial stack 30 isremoved, thus exposing a portion of the upper surface of the secondp-type contact electrode 35 p. In this case, the side of the secondepitaxial stack 30 is obliquely patterned with respect to the uppersurface of the substrate 10, and the angle formed between the secondepitaxial stack 30 and upper surface of the substrate 10 may be betweenabout 45 degrees and about 85 degrees.

Then, portions of the second p-type contact electrode 35 p, the secondadhesive layer 63, and the second wavelength pass filter 73 areadditionally removed, exposing the upper surface of the third p-typecontact electrode 45 p. Further, in the fourth contact hole CH4 of thethird contact 40C, portions of the second p-type contact electrode 35 p,the second adhesive layer 63, the second wavelength pass filter 73, andthe third epitaxial stack 40 are removed, exposing the upper surface ofthe n-type semiconductor layer of the third epitaxial stack 40. Thethird epitaxial stack 40 is additionally removed from the region exceptfor the light emitting region.

The sides of the third epitaxial stack 40, the second adhesive layer 63,the second wavelength pass filter 73, and the third p-type contactelectrode 45 p are obliquely patterned with respect to the upper surfaceof the substrate 10. Specifically, the angle formed between the thirdepitaxial stack 40 and upper side of the substrate 10 may be betweenabout 45 degrees and about 85 degrees.

Next, the second optically non-transmissive film 85 is formed on thesubstrate 10 that is formed with the contact holes, or the like. Sincethe other components including the first to third epitaxial stacks 20,30, and 40 are inclined, the second optically non-transmissive film 85may be formed with a sufficient thickness along the inclined sides. Ingeneral, it may be difficult to form the second opticallynon-transmissive film 85 with a sufficient thickness if the othercomponents including the first to third epitaxial stacks 20, 30, and 40have vertical or nearly vertical sides. The second opticallynon-transmissive film 85 may also be a DBR or an organic polymer filmhaving a black color. In an exemplary embodiment, a floating metalreflective film may further be provided on the first opticallynon-transmissive film 83. In an exemplary embodiment, the opticallynon-transmissive film may be formed by depositing two or more insulatingfilms having refractive indices different from each other.

The second optically non-transmissive film 85 is formed on the frontside of the substrate 10 and then patterned to expose underlyingcomponents in some regions. Accordingly, the second opticallynon-transmissive film 85 has the first ‘contact hole CH1’ partiallyexposing the upper surface of the first p-type contact electrode 25 p atthe common contact 50C, the first contact hole CH1 exposing the uppersurfaces of the second and third n-type contact electrodes, the secondcontact hole CH2 exposing the upper surface of the first n-type contactelectrode 21 n at the first contact 20C, the third contact hole CH3exposing the upper surface of the n-type semiconductor layer of thesecond epitaxial stack 30 at the second contact 30C, and fourth contacthole CH4 exposing the upper surface of the n-type semiconductor layer ofthe third epitaxial stack 40 at the third contact 40C.

Referring to FIGS. 33 and 34, the common pad 50P and the first to thirdpads 20P, 30,P and 40P are then formed in the common contact 50C formedwith the first to fourth contact holes CH1, CH2, CH3, and CH4, and inthe first to third contacts 20C, 30C, and 40C.

According to an exemplary embodiment, irregularities may be selectivelyprovided on the lower surfaces of the first to third epitaxial stacks20, 30, and 40. Each of the irregularities may be provided only at aportion corresponding to the light emitting region.

Further, according to an exemplary embodiment, an additional opticallynon-transmissive film may be further provided on the side of the lightemitting stacked structure.

By providing the optically non-transmissive film on the sides of thelight emitting stacked structure, it is possible to prevent thephenomenon in which light emitted from a certain light emitting stackedstructure affects adjacent light emitting stacked structures, or thephenomenon in which color is mixed with the light emitted from theadjacent light emitting stacked structures.

As described above, since the common voltage and the light emittingsignal are applied to the common contact 50C and the first to thirdcontacts 20C, 30C, and 40C, respectively, whether or not to emit thelight at the first to third epitaxial stacks 20, 30, and 40 can beindependently controlled, and as a result, various colors can beimplemented using emission of light from each of the epitaxial stacks.

FIG. 35 is a schematic plan view of a display apparatus according to anexemplary embodiment. FIG. 36 is a schematic cross-sectional view of anLED pixel for a display according to an exemplary embodiment.

Referring to FIGS. 35 and 36, a display apparatus 201 includes a circuitboard 251 and a plurality of pixels 200. Each of the pixels 200 mayinclude a substrate 221, and a first sub-pixel R, a second sub-pixel G,and a third sub-pixel B disposed on the substrate 221. In anotherexemplary embodiment, the substrate 221 may be omitted.

The circuit board 251 may have a passive circuit or an active circuit.For example, the passive circuit may include data lines and scan lines.For example, the active circuit may include a transistor and/or acapacitor. The circuit board 251 may have a circuit located on a surfacethereof or located therein. The circuit board 251 may include, forexample, a glass substrate, a sapphire substrate, a Si substrate, or aGe substrate.

The substrate 221 may support the first through third sub-pixels R, G,and B. When the substrate 221 is omitted, the first through thirdsub-pixels R, G, and B may be supported by the circuit board 251. Thesubstrate 221 may be formed continuously over the plurality of pixels200 and electrically connect the first through third sub-pixels R, G,and B to the circuit board 251. The substrate 221 may be, for example, aGaAs substrate, but is not limited thereto.

The first sub-pixel R includes a first LED stack 223, the secondsub-pixel G includes a second LED stack 233, and the third sub-pixel Bincludes a third LED stack 243. The first sub-pixel R is configured sothat light is emitted from the first LED stack 223, the second sub-pixelG is configured so that light is emitted from the second LED stack 233,and the third sub-pixel B is configured so that light is emitted fromthe third LED stack 243. The first through third LED stacks 223, 233,and 243 may be driven independently of each other.

The first LED stack 223, the second LED stack 233, and the third LEDstack 243 are stacked in a vertical direction to overlap each other. Thesecond LED stack 233 may be disposed on a partial region of the firstLED stack 223. The second LED stack 233 may disposed toward one side onthe first LED stack 223. The third LED stack 243 may be disposed on apartial region of the second LED stack 233. The third LED stack 243 maybe disposed toward one side on the second LED stack 233. However, theinventive concepts are not limited thereto, and the third LED stack 243may be disposed toward left side of the second LED stack 233.

Light R generated in the first LED stack 223 may be emitted from aregion that is not covered by the second LED stack 233, and light Ggenerated in the second LED stack 233 may be emitted from a region thatis not covered by the third LED stack 243. In particular, lightgenerated in the first LED stack 223 may be emitted to the outsidewithout passing through the second LED stack 233 and the third LED stack243, and light generated in the second LED stack 233 may be emitted tothe outside without passing through the third LED stack 243.

In addition, an area of a region from which the light R is emitted fromthe first LED stack 223, an area of a region from which the light G isemitted from the second LED stack 233, and an area of a region of thethird LED stack 243 may be different from each other, and an intensityof light emitted from each of the first through third LED stacks 223,233, and 243 may be adjusted by adjusting these areas.

However, the inventive concepts are not limited thereto. Light generatedin the first LED stack 223 may pass through the second LED stack 233 orpass through the second LED stack 233 and the third LED stack 243, andemitted to the outside. Light generated in the second LED stack 233 maypass through the third LED stack 243 and emitted to the outside.

Each of the first LED stack 223, the second LED stack 233, and the thirdLED stack 243 includes a first conductivity type semiconductor layer(for example, an n-type semiconductor layer), a second conductivity typesemiconductor layer (for example, a p-type semiconductor layer), and anactive layer interposed therebetween. The active layer may have, inparticular, a multiple quantum well structure. The first through thirdLED stacks 223, 233, and 243 may include different active layers, andthus may emit light of different wavelengths. For example, the first LEDstack 223 may be an inorganic LED emitting red light, the second LEDstack 233 may be an inorganic LED emitting green light, and the thirdLED stack 243 may be an inorganic LED emitting blue light. To this end,the first LED stack 223 may include an AlGaInP-based well layer, thesecond LED stack 233 may include an AlGaInP-based or AlGaInN-based welllayer, and the third LED stack 243 may include an AlGaInN-based welllayer. However, the inventive concepts are not limited thereto, and anorder of light emitted from the first LED stack 223, the second LEDstack 233, and the third LED stack 243 may be changed. For example, thefirst LED stack 223 may emit any one of red, green, and blue light, andthe second LED stack 233 and the third LED stack 243 may respectivelyemit a different one of the red, green, and blue light from each other.

In addition, a distribution Bragg reflector may be disposed between thesubstrate 221 and the first LED stack 223 to prevent light generated inthe first LED stack 223 from being absorbed by the substrate 221 andlost. For example, a distribution Bragg reflector formed by alternatelystacking an AlAs-based semiconductor layer and an AlGaAs-basedsemiconductor layer.

The third LED stack 243 and the second LED stack 233 may have inclinedside surfaces. The inclined side surfaces may enhance reliability of adisplay apparatus by increasing a step coverage of an insulating layeror an interconnection line, such as a connector, formed on a sidesurface of the LED stacks 233 and 243. The first LED stack 223 may alsohave an inclined side surface. As used herein, a connector may be anytype of structure, including through holes, vias, wires, lines,conductive material, and the like, that serves to electrically and/ormechanically connect two elements, such as layers.

FIGS. 37A and 37B are schematic circuit diagrams of a display apparatusaccording to exemplary embodiments.

Referring to FIG. 37A, a display apparatus according to an exemplaryembodiment may be driven in an active matrix manner. To this end, acircuit board may include an active circuit.

For example, a driving circuit according to an exemplary embodiment mayinclude two or more transistors, for example, transistors Tr1 and Tr2,and a capacitor. When a power source is connected to selection linesVrow1 through Vrow3, and when data voltage is applied to data linesVdata1 through Vdata3, voltage may be applied to a corresponding LED. Inaddition, a corresponding capacitor may be charged with electric chargesbased on values of the data lines Vdata1 through Vdata3. A state inwhich the transistor Tr2 is turned on may be maintained by the chargedvoltage of the capacitor, and accordingly, the voltage of the capacitormay be maintained and be applied to LEDs LED1 through LED3 even though apower supply to the line Vrow1 is cut off. In addition, current flowingin the LEDs LED1 through LED3 may be changed based on the values of thedata lines Vdata1 through Vdata3. Current may be supplied through Vdd atall times, and thus it is possible to continue to emit light.

The transistors Tr1 and Tr2 and the capacitor may be formed in thecircuit board 251. Here, the LEDs LED1 through LED3 may correspond tothe first through third LED stacks 223, 233, and 243 stacked in a singlepixel, respectively. Anodes of the first through third LED stacks 223,233, and 243 are connected to the transistors Tr2, and cathodes thereofmay be grounded. As shown in FIG. 37A, the cathodes of the first throughthird LED stacks 223, 233, and 243 may be connected in common andgrounded.

FIG. 37A shows a circuit diagram for active matrix driving, however, theinventive concepts are not limited thereto, and another circuit may beused. In addition, although anodes of the LEDs LED1 through LED3 aredescribed as being connected to different transistors (for example, thetransistors Tr2) and cathodes thereof are described as being grounded,according to some exemplary embodiments, the anodes of the first throughthird LED stacks 223, 233, and 243 may be connected in common, and thecathodes may be connected to different transistors.

FIG. 37B is a schematic circuit diagram for a passive matrix driving.

The circuit board 251 may include data lines, for example, Vdata1,Vdata2, Vdata3, and the like, and scan lines, for example, Vscan1-1,Vscan1-2, Vscan1-3, Vscan2-1, and the like. Each of first through thirdsub-pixels R, G, and B may be connected to a data line and a scan line.Anodes of the first through third sub-pixels R, G, and B may beconnected to different scan lines (for example, Vscan1-1, Vscan1-2 andVscan1-3), and cathodes thereof may be connected in common to the dataline Vdata1. However, the inventive concepts are not limited thereto,and anodes of the first through third sub-pixels R, G, and B may beconnected in common to a data line, and cathodes thereof may beconnected to different scan lines.

According to an exemplary embodiment, each of the first through thirdLED stacks 223, 233, and 243 may be driven by using a pulse-widthmodulation method or by changing a current intensity, so that abrightness of each sub-pixel may be adjusted. Furthermore, thebrightness may be adjusted by changing an area of each of the firstthrough third LED stacks 223, 233, and 243, and an area of a region fromwhich light R, G, and B is emitted in each of the first through thirdLED stacks 223, 233, and 243. For example, an area of an LED stack, forexample, the first LED stack 223, that emits light with low visibilitymay be greater than an area of the second LED stack 233 or an area ofthe third LED stack 243, so as to emit light with a higher intensityunder the same current density. Also, since the area of the second LEDstack 233 is greater than the area of the third LED stack 243, thesecond LED stack 233 may emit light with a higher intensity than that ofthe third LED stack 243 under the same current density. As such, anoutput of light may be controlled in consideration of visibility oflight emitted from the first LED stack 223, the second LED stack 233,and the third LED stack 243 by adjusting an area of each of the firstthrough third LED stacks 223, 233, and 243.

FIGS. 38A and 38B are an enlarged plan view and an enlarged bottom viewof one pixel region of a display apparatus according to an exemplaryembodiment, respectively. FIGS. 39A, 39B, 39C, and 39D are schematiccross-sectional views taken along dotted lines A-A, B-B, C-C, and D-D ofFIG. 38A, respectively.

A pixel of a display apparatus is disposed on a circuit board (forexample, the circuit board 251 of FIG. 35), and includes a substrate221, and first through third sub-pixels R, G and B. The substrate 221may be continuous over a plurality of pixels. Hereinafter, a singlepixel will be described in more detail.

Referring to FIGS. 38A, 38B, 39A, 39B, 39C, and 39D, a pixel may includea substrate 221, a distribution Bragg reflector 222, an insulating layer225, through-vias 227 a, 227 b, and 227 c, a first LED stack 223, asecond LED stack 233, a third LED stack 243, a first-1 ohmic electrode229 a, a first-2 ohmic electrode 229 b, a second-1 ohmic electrode 239,a second-2 ohmic electrode 235, a third-1 ohmic electrode 249, a third-2ohmic electrode 245, a first bonding layer 253, a second bonding layer255, an upper insulating layer 261, connectors 271, 272, and 273, alower insulating layer 275, and electrode pads 277 a, 277 b, 277 c, and277 d.

The first through third sub-pixels R, G, and B may include LED stacks223, 233, and 243, and ohmic electrodes, respectively. In addition,anodes of the first through third sub-pixels R, G, and B may beelectrically connected to the electrode pads 277 a, 277 b, and 277 c,respectively, and cathodes thereof may be electrically connected to theelectrode pad 277 d. Thus, the first through third sub-pixels R, G, andB may be driven independently of each other.

The substrate 221 supports the first through third LED stacks 223, 233,and 243. The substrate 221 may be a growth substrate capable of growingAlGaInP-based semiconductor layers, and may include, for example, a GaAssubstrate. In particular, the substrate 221 may be a semiconductorsubstrate, and may exhibit n-type conductivity.

The first LED stack 223 includes a first conductivity type semiconductorlayer 223 a and a second conductivity type semiconductor layer 223 b,and the second LED stack 233 includes a first conductivity typesemiconductor layer 233 a and a second conductivity type semiconductorlayer 233 b. The third LED stack 243 includes a first conductivity typesemiconductor layer 243 a and a second conductivity type semiconductorlayer 243 b. An active layer may be interposed between each of the firstconductivity type semiconductor layers 223 a, 233 a, and 243 a and eachof the second conductivity type semiconductor layers 223 b, 233 b, and243 b.

According to an exemplary embodiment, each of the first conductivitytype semiconductor layers 223 a, 233 a, and 243 a may be an n-typesemiconductor layer, and each of the second conductivity typesemiconductor layers 223 b, 233 b, and 243 b may be a p-typesemiconductor layer. A surface roughened by surface texturing (orirregularities) may be formed on an upper surface of each of the firstconductivity type semiconductor layers 223 a, 233 a, and 243 a. However,the inventive concepts are not limited thereto, and semiconductor typesof the first conductivity semiconductor layer and the secondconductivity semiconductor layer may be reversed.

The first LED stack 223 is disposed close to the circuit board 251, thesecond LED stack 233 is located on the first LED stack 223, and thethird LED stack 243 is located on the second LED stack 233. The secondLED stack 233 is disposed on a partial region of the first LED stack 223so that the first LED stack 223 partially overlaps the second LED stack233. The third LED stack 243 is disposed on a partial region of thesecond LED stack 233 so that the second LED stack 233 partially overlapsthe third LED stack 243. Thus, light generated in the first LED stack223 may be emitted to the outside without passing through the second andthird LED stacks 233 and 243. Also, light generated in the second LEDstack 233 may be emitted to the outside without passing through thethird LED stack 243.

Materials of the first LED stack 223, the second LED stack 233, and thethird LED stack 243 are substantially the same as those described withreference to FIG. 36, and accordingly, duplicated descriptions thereofwill be omitted to avoid redundancy.

The first LED stack 223 has an inclined side surface. As used herein,the “inclined side surface” may refer to a surface that is notperpendicular to an upper surface or a lower surface of the first LEDstack 223, and in particular, which forms an inclination angle between aside surface and the lower surface of the first LED stack 223 less thanabout 90 degrees. The second LED stack 233 and the third LED stack 243may also include inclined side surfaces. In particular, a side surfaceof the second LED stack 233 may have an angle of inclination less than90 degrees with respect to a lower surface of the second LED stack 233,and a side surface of the third LED stack 243 may also have an angle ofinclination less than 90 degrees with respect to a lower surface of thethird LED stack 243.

While FIG. 39A shows that all the first through third LED stacks 223,233, and 243 have inclined side surfaces, however, the inventiveconcepts are not limited thereto. For example, at least one of the firstthrough third LED stacks 223, 233, and 243 may not have an inclined sidesurface. Furthermore, according to some exemplary embodiments, only aportion of the side surface of the first LED stack 223, the second LEDstack 233, or the third LED 243 may be inclined.

The distribution Bragg reflector 222 is interposed between the substrate221 and the first LED stack 223. The distribution Bragg reflector 222may be formed with semiconductor layers grown on the substrate 221. Forexample, the distribution Bragg reflector 222 may be formed byalternately stacking an AlAs layer and an AlGaAs layer. The distributionBragg reflector 222 may be semiconductor layers, which electricallyconnects the substrate 221 and the first conductivity type semiconductorlayer 223 a of the first LED stack 223. The distribution Bragg reflector222 may also have an inclined side surface, but is not limited thereto.

The through-vias 227 a, 227 b, and 227 c that pass through the substrate221 may be formed. The through-vias 227 a, 227 b, and 227 c may alsopass through the first LED stack 223. The through-vias 227 a, 227 b, and227 c may be formed of a conductive paste or by plating. Although thethrough-vias 227 a, 227 b, and 227 c are shown as having a constantwidth, the inventive concepts are not limited thereto. Widths of thethrough-vias 227 a, 227 b, and 227 c may be varied along horizontal orvertical direction. For example, the widths of the through-vias 227 a,227 b, and 227 c may decrease from top to bottom of the substrate 221.

The insulating layer 225 is disposed between the through-vias 227 a, 227b, and 227 c and an inner wall of a through-hole passing through thesubstrate 221 and the first LED stack 223, to prevent the through-vias227 a, 227 b, and 227 c from being short-circuited to the substrate 221and the first LED stack 223.

The first-1 ohmic electrode 229 a is in ohmic contact with the firstconductivity type semiconductor layer 223 a of the first LED stack 223.The first-1 ohmic electrode 229 a may be formed of, for example, anAu—Te alloy or an Au—Ge alloy.

To form the first-1 ohmic electrode 229 a, the second conductivity typesemiconductor layer 223 b and the active layer may be partially removed,and the first conductivity type semiconductor layer 223 a may beexposed. The first-1 ohmic electrode 229 a may be disposed away from aregion in which the second LED stack 233 is disposed. In addition, thefirst-1 ohmic electrode 229 a may include a pad region and an extension,and the connector 271 may be connected to the pad region as shown inFIG. 38A.

The first-2 ohmic electrode 229 b is in ohmic contact with the secondconductivity type semiconductor layer 223 b of the first LED stack 223.For current dispersion, the first-2 ohmic electrode 229 b may be formedto partially surround the first-1 ohmic electrode 229 a, as shown inFIG. 38A. However, the first-2 ohmic electrode 229 b is not necessarilyformed to have an extension. The first-2 ohmic electrode 229 b may beformed of, for example, an Au—Zn alloy, an Au—Be alloy, or others. Inaddition, the first-2 ohmic electrode 229 b may be formed as a singlelayer, but is not limited thereto, and may be formed of multiple layers.

The first-2 ohmic electrode 229 b may be connected to the through-via227 a, and accordingly, the through-via 227 a may be electricallyconnected to the second conductivity type semiconductor layer 223 b.

The second-1 ohmic electrode 239 is in ohmic contact with the firstconductivity type semiconductor layer 233 a of the second LED stack 233.The second-1 ohmic electrode 239 may also include a pad region and anextension. The connector 271 may electrically connect the second-1 ohmicelectrode 239 to the first-1 ohmic electrode 229 a, as shown in FIG.38A. The second-1 ohmic electrode 239 may be disposed away from a regionin which the third LED stack 243 is disposed.

The second-2 ohmic electrode 235 is in ohmic contact with the secondconductivity type semiconductor layer 233 b of the second LED stack 233.The second-2 ohmic electrode 235 may include a reflective layer 235 aand a barrier layer 235 b. The reflective layer 235 a may reflect lightgenerated in the second LED stack 233 to enhance a light efficiency ofthe second LED stack 233. The barrier layer 235 b may protect thereflective layer 235 a, and may function as a connection pad to whichthe connector 272 is connected. The second-2 ohmic electrode 235 may beformed of, for example, a metal layer, but is not limited thereto. Forexample, the second-2 ohmic electrode 235 may be formed of a transparentconductive layer such as a conductive oxide semiconductor layer.

The third-1 ohmic electrode 249 is in ohmic contact with the firstconductivity type semiconductor layer 243 a of the third LED stack 243.The third-1 ohmic electrode 249 may also include a pad region and anextension. The connector 271 may connect the third-1 ohmic electrode 249to the first-1 ohmic electrode 229 a, as shown in FIG. 38A.

The third-2 ohmic electrode 245 is in ohmic contact with the secondconductivity type semiconductor layer 243 b of the third LED stack 243.The third-2 ohmic electrode 245 may include a reflective layer 245 a anda barrier layer 245 b. The reflective layer 245 a may reflect lightgenerated in the third LED stack 243 to enhance a light efficiency ofthe third LED stack 243. The barrier layer 245 b may protect thereflective layer 245 a, and may function as a connection pad to whichthe connector 273 is connected. The third-2 ohmic electrode 245 may beformed of, for example, a metal layer, but is not limited thereto. Forexample, the third-2 ohmic electrode 245 may be formed of a transparentconductive layer such as a conductive oxide semiconductor layer.

The first-2 ohmic electrode 229 b, the second-2 ohmic electrode 235, andthe third-2 ohmic electrode 245 may be in ohmic contact with p-typesemiconductor layers of the LED stacks, respectively, to help currentspreading. The first-1 ohmic electrode 229 a, the second-1 ohmicelectrode 239, and the third-1 ohmic electrode 249 may be in ohmiccontact with n-type semiconductor layers of the LED stacks,respectively, to help current dispersion.

The first bonding layer 253 couples the second LED stack 233 to thefirst LED stack 223. The second-2 ohmic electrode 235 may be in contactwith the first bonding layer 253. The first bonding layer 253 may belight transmissive or light non-transmissive. The first bonding layer253 may be formed of an organic material layer, or an inorganic materiallayer. The organic material layer may include, for example, SU8,poly(methyl methacrylate) (PMMA), polyimide, parylene, benzocyclobutene(BCB), or others, and the inorganic material layer may include, forexample, Al₂O₃, SiO₂, SiN_(x), or others. The organic material layer maybe bonded at a high vacuum and high pressure. The inorganic materiallayers may be surface-planarized by, for example, a chemical mechanicalpolishing process, then surface energy may be controlled by usingplasma, or others, and may be bonded at high vacuum using the surfaceenergy. The first bonding layer 253 may also be formed by aspin-on-glass method, and may be formed as a metal bonding layer, suchas AuSn. When a metal bonding layer is adopted, an insulating layer forelectrical insulation of the first LED stack and the metal bonding layermay be disposed on the first LED stack 223. Furthermore, to preventlight generated in the first LED stack 223 from being incident to thesecond LED stack 233, a reflective layer may be added between the firstbonding layer 253 and the first LED stack 223.

The first bonding layer 253 may also have an inclined side surface. Inparticular, the first bonding layer 253 may have an angle of inclinationless than about 90 degrees with respect to the upper surface of thefirst LED stack 223. Although the angle of inclination of the firstbonding layer 253 may be substantially the same as an angle ofinclination of the second LED stack 233, the inventive concepts are notlimited thereto. For example, the angle of inclination of the firstbonding layer 253 may be different from the angle of inclination of thesecond LED stack 233. In an exemplary embodiment, the angle ofinclination of the second LED stack 233 may be greater than the angle ofinclination of the first bonding layer 253, and accordingly, it ispossible to enhance a step coverage of the connectors 271, 272, and 273or the insulating layer 261 formed on a side surface of the second LEDstack 233 and/or a side surface of the first bonding layer 253. Inanother exemplary embodiment, the angle of inclination of the second LEDstack 233 may be less than the angle of inclination of the first bondinglayer 253, and accordingly, it is possible to increase a light emittingarea of the second LED stack 233.

The second bonding layer 255 couples the second LED stack 233 and thethird LED stack 243. The second bonding layer 255 may be disposedbetween the second LED stack 233 and the third-2 ohmic electrode 245,and may bond the second LED stack 233 and the third-2 ohmic electrode245. The second bonding layer 255 may also be formed of a bondingmaterial. In addition, an insulating layer and/or a reflective layer maybe added between the second LED stack 233 and the second bonding layer255.

The second bonding layer 255 may also have an inclined side surface. Inparticular, the second bonding layer 255 may have an angle ofinclination less than about 90 degrees with respect to the upper surfaceof the second LED stack 233. Although the angle of inclination of thesecond bonding layer 255 may be substantially the same as an angle ofinclination of the third LED stack 243, the inventive concepts are notlimited thereto. For example, the angle of inclination of the secondbonding layer 255 may be different from the angle of inclination of thethird LED stack 243. In an exemplary embodiment, the angle ofinclination of the third LED stack 243 may be greater than the angle ofinclination of the second bonding layer 255, and accordingly, it ispossible to enhance a step coverage of the connectors 271 and 273 or theinsulating layer 261 formed on a side surface of the third LED stack 243and/or a side surface of the second bonding layer 255. In anotherexemplary embodiment, the angle of inclination of the third LED stack243 may be less than the angle of inclination of the second bondinglayer 255, and accordingly, it is possible to increase a light emittingarea of the third LED stack 243.

When the first bonding layer 253 and the second bonding layer 255 areformed of light transmissive materials, and when the second-2 ohmicelectrode 235 and the third-2 ohmic electrode 245 are formed withtransparent oxide layers, a portion of light generated in the first LEDstack 223 may pass through the first bonding layer 253 and the second-2ohmic electrode 235, may be incident to the second LED stack 233, andthen may be emitted to the outside through the second LED stack 233.Also, a portion of light generated in the first LED stack 223 may passthrough the second bonding layer 255 and the third-2 ohmic electrode245, may be incident to the third LED stack 243, and then may be emittedto the outside. In addition, a portion of light generated in the secondLED stack 233 may pass through the second bonding layer 255 and thethird-2 ohmic electrode 245, may be incident to the third LED stack 243,and then may be emitted to the outside.

In this case, there is a need to prevent the light generated in thefirst LED stack 223 from being absorbed by the second LED stack 233while the light passing through the second LED stack 233. To this end,light generated in the first LED stack 223 may need to have a smallerenergy than a band gap energy of the second LED stack 233, and thus, awavelength of light generated in the first LED stack 223 may be longerthan that of light generated in the second LED stack 233.

In addition, to prevent light generated in the second LED stack 233 frombeing absorbed by the third LED stack 243 while the light passingthrough the third LED stack 243, light generated in the second LED stack233 may have a wavelength longer than that of light generated in thethird LED stack 243.

Meanwhile, when the first bonding layer 253 and the second bonding layer255 are non-transmissive to light, reflective layers may be interposedbetween the first LED stack 223 and the first bonding layer 253, andbetween the second LED stack 233 and the second bonding layer 255,respectively, to reflect light generated in the first LED stack 223 andincident to the first bonding layer 253, and light generated in thesecond LED stack 233 and incident to the second bonding layer 255. Thereflected light may be emitted to the outside through the first LEDstack 223 and the second LED stack 233, respectively.

The upper insulating layer 261 may substantially cover the first throughthird LED stacks 223, 233, and 243. The upper insulating layer 261 maycover, in particular, an inclined side surface of each of the second LEDstack 233 and the third LED stack 243, and may also cover a side surfaceof the first LED stack 223.

The upper insulating layer 261 may have openings that expose the firstthrough third through-vias 227 a, 227 b, and 227 c, and also haveopenings that expose the first conductivity type semiconductor layer 233a of the second LED stack 223, the first conductivity type semiconductorlayer 243 a of the third LED stack 243, the second-2 ohmic electrode235, and the third-2 ohmic electrode 245.

The upper insulating layer 261 may be, but is not particularly limitedto, an insulating material layer, and may be formed of, for example,silicon oxide or silicon nitride. The upper insulating layer 261 may beformed using a chemical vapor deposition technique, but is not limitedthereto, and may be formed using a sputtering technique. In particular,when an angle of inclination of the first bonding layer 253 (or thesecond bonding layer 255) is greater than an angle of inclination of thesecond LED stack 233 (or the third LED stack 243), a step coverage maybe improved by using the sputtering technique.

The connector 271 electrically connects the first-1 ohmic electrode 229a, the second-1 ohmic electrode 239, and the third-1 ohmic electrode 249to each other. The connector 271 is formed on the upper insulating layer261, and is insulated from the second conductivity type semiconductorlayer 243 b of the third LED stack 243, the second conductivity typesemiconductor layer 233 b of the second LED stack 233, and the secondconductivity type semiconductor layer 223 b of the first LED stack 223.

The connector 271 may be formed of substantially the same material asthose of the second-1 ohmic electrode 239 and the third-1 ohmicelectrode 249, and thus may be formed together with the second-1 ohmicelectrode 239 and the third-1 ohmic electrode 249. However, theinventive concepts are not limited thereto, and the connector 271 may beformed of a conductive layer different from the second-1 ohmic electrode239 or the third-1 ohmic electrode 249, and thus, may be formed in aprocess separate from a process for forming the second-1 ohmic electrode239 and/or the third-1 ohmic electrode 249.

As shown in FIG. 39A, the connector 271 may be formed on inclined sidesurfaces of the second and third LED stacks 233 and 243 and the firstand second bonding layers 253 and 255. Since the second and third LEDstacks 233 and 243 and the first and second bonding layers 253 and 255have the inclined side surfaces, the likelihood of disconnection of theconnector 271 may be reduced or prevented as compared to when the secondand third LED stacks 233 and 243 and the first and second bonding layers253 and 255 have vertical side surfaces, and thus, reliability of apixel may be enhanced.

The connector 272 may electrically connect the second-2 ohmic electrode235, for example, the barrier layer 235 b, and the second through-via227 b. The connector 273 electrically connects the third-2 ohmicelectrode 245, for example, the barrier layer 245 b, and the thirdthrough-via 227 c. The connector 272 may be insulated from the first LEDstack 223 by the upper insulating layer 261. The connector 273 may alsobe insulated from the second LED stack 233 and the first LED stack 223by the upper insulating layer 261.

As shown in FIG. 39C, the connector 272 may be formed on the inclinedside surface of the first bonding layer 253, and accordingly, anoccurrence of disconnection of the connector 272 may be prevented ascompared to when the first bonding layer 253 has a vertical sidesurface. In addition, as shown in FIG. 39D, the connector 273 may beformed on side surfaces of the second bonding layer 255, the second LEDstack 233 and the first bonding layer 253, and the second bonding layer255, the second LED stack 233, and the first bonding layer 253 have theinclined side surfaces, and accordingly, an occurrence of disconnectionof the connector 273 may be prevented.

The connectors 272 and 273 may be formed together in the same process.The connectors 272 and 273 may also be formed together with theconnector 271. Furthermore, the connectors 272 and 273 may be formed ofsubstantially the same material as those of the second-1 ohmic electrode239 and the third-1 ohmic electrode 249 together with the second-1 ohmicelectrode 239 and the third-1 ohmic electrode 249. However, theinventive concepts are not limited thereto, and the connectors 272 and273 may be formed of conductive layers different from the second-1 ohmicelectrode 239 or the third-1 ohmic electrode 249, and thus, may beformed in a process separate from a process for forming the second-1ohmic electrode 239 and/or the third-1 ohmic electrode 249.

The lower insulating layer 275 covers a bottom surface of the substrate221. The lower insulating layer 275 may have openings that expose thefirst through third through-vias 227 a, 227 b, and 227 c under thesubstrate 221, and also have an opening that exposes the bottom surfaceof the substrate 221.

The electrode pads 277 a, 277 b, 277 c, and 277 d are disposed under thesubstrate 221. The electrode pads 277 a, 277 b, and 277 c are connectedto the through-vias 227 a, 227 b, and 227 c through the openings of thelower insulating layer 275, respectively, and the electrode pad 277 d isconnected to the substrate 221.

The electrode pads 277 a, 277 b, and 277 c are disposed for each pixeland are electrically connected to first through third LED stacks 223,233, and 243 of each pixel. The electrode pad 277 d may be disposed foreach pixel. However, since the substrate 221 is disposed continuouslyover a plurality of pixels, the electrode pad 277 d may not need to bedisposed for each pixel.

By bonding the electrode pads 277 a, 277 b, 277 c, and 277 d to thecircuit board 251, a display apparatus according to an exemplaryembodiment may be provided.

Hereinafter, a method of manufacturing a display apparatus according anexemplary embodiment will be described.

FIGS. 40A through 47B are plan views and cross-sectional viewsschematically illustrating a method of manufacturing a display apparatusaccording to an exemplary embodiment. Each of the cross-sectional viewsis taken along line E-E of a corresponding plan view.

Referring to FIGS. 40A and 40B, a first LED stack 223 is grown on asubstrate 221. The substrate 221 may be, for example, a GaAs substrate.The first LED stack 223 is formed with AlGaInP-based semiconductorlayers, and includes a first conductivity type semiconductor layer 223a, an active layer, and a second conductivity type semiconductor layer223 b. Before the first LED stack 223 is grown, a distribution Braggreflector 222 may be formed first on the substrate 221. The distributionBragg reflector 222 may have, for example, a stack structure ofalternating AlAs and AlGaAs layers.

Next, grooves are formed on the substrate 221 and the first LED stack223 using a photolithography and etching process. The grooves may passthrough the substrate 221, or may be formed to have a height less than athickness of the substrate 221, as shown in the drawings.

Next, an insulating layer 225 covering a side wall of each of thegrooves is formed, and through-vias 227 a, 227 b and 227 c filling thegrooves are formed. For example, after an insulating layer 225 coveringa side wall of each of the grooves is formed, the through-vias 227 a,227 b, and 227 c may be formed by filling the grooves with a conductivelayer using a plating technique, or filling the grooves with aconductive paste, and by removing a conductive material layer and aninsulating layer remaining on an upper surface of the first LED stack223 using a chemical mechanical polishing technique, or the like.

Referring to FIGS. 41A and 41B, a second LED stack 233 and a second-2ohmic electrode 235 may be bonded to the first LED stack 223 through afirst bonding layer 253.

The second LED stack 233 is grown on a second substrate, and thesecond-2 ohmic electrode 235 is formed on the second LED stack 233. Thesecond LED stack 233 may be formed with AlGaInP-based semiconductorlayers or AlGaInN-based semiconductor layers, and may include a firstconductivity type semiconductor layer 233 a, an active layer, and asecond conductivity type semiconductor layer 233 b. The second substratemay be a substrate, for example, a GaAs substrate, capable of growingAlGaInP-based semiconductor layers, or a sapphire substrate, capable ofgrowing AlGaInN-based semiconductor layers. A composition ratio of Al,Ga, and In may be set so that the second LED stack 233 may emit greenlight. The second-2 ohmic electrode 235 is in ohmic contact with thesecond conductivity type semiconductor layer 233 b, for example, ap-type semiconductor layer. The second-2 ohmic electrode 235 may includea reflective layer 235 a for reflecting light generated in the secondLED stack 233, and a barrier layer 235 b.

The second-2 ohmic electrode 235 is disposed to face the first LED stack223 and is bonded to the first LED stack 223 by the first bonding layer253. Next, the second substrate is removed from the second LED stack 233using a chemical etching technique or a laser lift-off technique, andthe first conductivity type semiconductor layer 233 a is exposed. Asurface roughened by surface texturing may be formed on the exposedfirst conductivity type semiconductor layer 233 a.

According to an exemplary embodiment, before the first bonding layer 253is formed, an insulating layer and a reflective layer may be added ontothe first LED stack 223.

Referring to FIGS. 42A and 42B, a third LED stack 243 and a third-2ohmic electrode 245 may be bonded to the second LED stack 233 through asecond bonding layer 255.

First, the third LED stack 243 is grown on a third substrate, and thethird-2 ohmic electrode 245 is formed on the third LED stack 243. Thethird LED stack 243 may be formed with AlGaInN-based semiconductorlayers, and may include a first conductivity type semiconductor layer243 a, an active layer, and a second conductivity type semiconductorlayer 243 b. The third substrate is a substrate capable of growing agallium nitride-based semiconductor layer, and is different from thefirst substrate 221. A composition ratio of AlGaInN may be set so thatthe third LED stack 243 may emit blue light. The third-2 ohmic electrode245 is in ohmic contact with the second conductivity type semiconductorlayer 243 b, for example, a p-type semiconductor layer. The third-2ohmic electrode 245 may include a reflective layer 245 a for reflectinglight generated in the third LED stack 243, and a barrier layer 245 b.

The third-2 ohmic electrode 245 is disposed to face the second LED stack233 and is bonded to the second LED stack 233 by the second bondinglayer 255. Next, the third substrate is removed from the third LED stack243 using a chemical lift-off technique or a laser lift-off technique,and the first conductivity type semiconductor layer 243 a is exposed. Asurface roughened by surface texturing may be formed on the exposedfirst conductivity type semiconductor layer 243 a.

According to an exemplary embodiment, before the second bonding layer255 is formed, an insulating layer and a reflective layer may be addedonto the second LED stack 233.

Referring to FIGS. 43A and 43B, in each pixel region, the third LEDstack 243 is removed except a region of a third sub-pixel B bypatterning the third LED stack 243. In addition, in the region of thethird sub-pixel B, an indented part may be formed in the third LED stack243, and the barrier layer 245 b may be exposed in the indented part.The third LED stack 243 is formed to have an inclined side surface, asshown in FIG. 43B. For example, a photoresist pattern with an inclinedside surface may be formed using a reflow process of a photoresist, andthe third LED stack 243 may be etched using the photoresist pattern withthe inclined side surface, so that the third LED stack 243 having theinclined side surface may be formed.

Next, in regions other than the region of the third sub-pixel B, thethird-2 ohmic electrode 245 and the second bonding layer 255 areremoved, and the second LED stack 233 is exposed. The third-2 ohmicelectrode 245 and the second bonding layer 255 may also be formed tohave inclined side surfaces. In particular, an angle of inclination of aside surface of the second bonding layer 255 may be substantially thesame as an angle of inclination of a side surface of the third LED stack243, but is not limited thereto. The third-2 ohmic electrode 245 isrestricted near the region of the third sub-pixel B.

Meanwhile, in each pixel region, the second LED stack 233 is removedfrom regions except a region of a second sub-pixel G of each pixel bypatterning the second LED stack 233. A second LED stack 233 of theregion of the second sub-pixel G partially overlaps the third LED stack243. As shown in FIG. 43B, the second LED stack 233 is also patterned tohave an inclined side surface.

By patterning the second LED stack 233, the second-2 ohmic electrode 235is exposed. The second LED stack 233 may include an indented part, andthe second-2 ohmic electrode 235, for example, the barrier layer 235 b,may be exposed in the indented part.

Next, the second-2 ohmic electrode 235 and the first bonding layer 253are removed, and the first LED stack 223 is exposed. The second-2 ohmicelectrode 235 and the first bonding layer 253 may also be patterned tohave inclined side surfaces. In particular, an angle of inclination of aside surface of the first bonding layer 253 may be substantially thesame as an angle of inclination of a side surface of the second LEDstack 233, but is not limited thereto. The second-2 ohmic electrode 235is restricted near the region of the second sub-pixel G. In addition,the first through third through-vias 227 a, 227 b, and 227 c may beexposed together when the first LED stack 223 is exposed.

Meanwhile, in each pixel region, the first conductivity typesemiconductor layer 223 a is exposed by patterning the secondconductivity type semiconductor layer 223 b of the first LED stack 223.The first conductivity type semiconductor layer 223 a may be exposed tohave substantially an elongated shape, as shown in FIG. 43A, but is notlimited thereto.

Furthermore, pixel regions may be separated by patterning the first LEDstack 223. Accordingly, a region of a first sub-pixel R is defined.Here, the distribution Bragg reflector 222 may also be divided. As shownin FIG. 43B, the first LED stack 223 may be patterned to have aninclined side surface, and the distribution Bragg reflector 222 may alsohave an inclined side surface. However, the inventive concepts are notlimited thereto. For example, the distribution Bragg reflector 222 maybe continuous over a plurality of pixels instead of being divided.Furthermore, the first LED stack 223 may have substantially a verticalside surface. Moreover, the first conductivity type semiconductor layer223 a may be continuous over a plurality of pixels instead of beingdivided into pixel regions.

Referring to FIGS. 44A and 44B, a first-1 ohmic electrode 229 a and afirst-2 ohmic electrode 229 b are formed on the first LED stack 223. Thefirst-1 ohmic electrode 229 a may be formed of, for example, an Au—Tealloy, an Au—Ge alloy, or others, on the exposed first conductivity typesemiconductor layer 223 a. The first-2 ohmic electrode 229 b may beformed of, for example, an Au—Be alloy, an Au—Zn alloy, or others, onthe second conductivity type semiconductor layer 223 b. The first-2ohmic electrode 229 b may be formed first, and the first-1 ohmicelectrode 229 a may be formed, or the first-1 ohmic electrode 229 a maybe formed before the first-2 ohmic electrode 229 b is formed. Thefirst-2 ohmic electrode 229 b may be connected to the first through-via227 a. The first-1 ohmic electrode 229 a may include a pad region and anextension, and the extension may extend from the pad region toward thefirst through-via 227 a.

In addition, for current spreading, the first-2 ohmic electrode 229 bmay be disposed to at least partially surround the first-1 ohmicelectrode 229 a. The first-1 ohmic electrode 229 a and the first-2 ohmicelectrode 229 b are formed to have an extended length as shown in thedrawings, however, the inventive concepts are not limited thereto. Forexample, the first-1 ohmic electrode 229 a and the first-2 ohmicelectrode 229 b may be formed to have substantially a circular shape.

Referring to FIGS. 45A and 45B, an upper insulating layer 261 coveringthe first through third LED stacks 223, 233, and 243 is formed. Theupper insulating layer 261 may cover the first-1 ohmic electrode 229 aand the first-2 ohmic electrode 229 b. The upper insulating layer 261may also cover side surfaces of the first through third LED stacks 223,233, and 243, and may cover a side surface of the distribution Braggreflector 222. The upper insulating layer 261 may be formed using achemical vapor deposition technique. According to some exemplaryembodiments, the upper insulating layer 261 may be formed using asputtering technique.

The upper insulating layer 261 may have an opening 261 a that exposesthe first-1 ohmic electrode 229 a, openings 261 b and 261 c that exposethe barrier layers 235 b and 245 b, openings 261 d and 261 e that exposethe second and third through-vias 227 b and 227 c, and openings 261 fand 261 g that expose the first conductivity type semiconductor layer233 a of the second LED stack 233 and the first conductivity typesemiconductor layer 243 a of the third LED stack 243. The openings 261 athrough 261 g may be formed using a photolithography and etchingtechnique.

Referring to FIGS. 46A and 46B, a second-1 ohmic electrode 239, athird-1 ohmic electrode 249, and connectors 271, 272, and 273 areformed. The second-1 ohmic electrode 239 is formed in the opening 261 fand is in ohmic contact with the first conductivity type semiconductorlayer 233 a. The third-1 ohmic electrode 249 is formed in the opening261 g and is in ohmic contact with the first conductivity typesemiconductor layer 243 a.

The connector 271 electrically connects the second-1 ohmic electrode 239and the third-1 ohmic electrode 249 to the first-1 ohmic electrode 229a. For example, the connector 271 may be connected to the first-1 ohmicelectrode 229 a exposed by the opening 261 a. The connector 271 isformed on the upper insulating layer 261 and is insulated from thesecond conductivity type semiconductor layers 223 b, 233 b and 243 b.

The connector 272 electrically connects the second-2 ohmic electrode 235to the second through-via 227 b, and the connector 273 electricallyconnects the third-2 ohmic electrode 245 to the third through-via 227 c.The connectors 272 and 273 are also disposed on the upper insulatinglayer 261, to prevent a short-circuit to the first through third LEDstacks 223, 233 and 243.

The connectors 271, 272, and 273 are formed on the inclined sidesurfaces of the first and second bonding layers 253 and 255, the secondLED stack 233 and the third LED stack 243, and thus, it is possible toprevent disconnection due to poor step coverage.

The second-1 ohmic electrode 239, the third-1 ohmic electrode 249, andthe connectors 271, 272, and 273 may be formed of substantially the samematerial together in the same process. However, the inventive conceptsare not limited thereto, and the connectors 271, 272, and 273 may beformed of different materials in different processes.

Next, referring to FIGS. 47A and 47B, a lower insulating layer 275 isformed to under the substrate 221. The lower insulating layer 275 mayhave openings that expose the first through third through-vias 227 a,227 b, and 227 c, and an opening(s) exposing the bottom surface of thesubstrate 221.

Electrode pads 277 a, 277 b, 277 c, and 277 d are formed on the lowerinsulating layer 275. The electrode pads 277 a, 277 b and 277 c areconnected to the first through third through-vias 227 a, 227 b, and 227c, respectively, and the electrode pad 277 d is connected to thesubstrate 221.

Accordingly, the electrode pad 277 a is electrically connected to thesecond conductivity type semiconductor layer 223 b of the first LEDstack 223 through the first through-via 227 a, the electrode pad 277 bis electrically connected to the second conductivity type semiconductorlayer 233 b of the second LED stack 233 through the second through-via227 b, and the electrode pad 277 c is electrically connected to thesecond conductivity type semiconductor layer 243 b of the third LEDstack 243 through the third through-via 227 c. The first conductivitytype semiconductor layers 223 a, 233 a, and 243 a of the first throughthird LED stacks 223, 233, and 243 are electrically connected in commonto the electrode pad 277 d.

The electrode pads 277 a, 277 b, 277 c, and 277 d of the substrate 221are bonded to the circuit board 251 of FIG. 35, so that a displayapparatus according to an exemplary embodiment may be provided. Thecircuit board 251 may include an active circuit or a passive circuit,and accordingly, the display apparatus may be driven in an active matrixdriving manner or a passive matrix driving manner.

FIG. 48 is a schematic cross-sectional view of an LED pixel for adisplay according to another exemplary embodiment.

Referring to FIG. 48, the LED pixel 202 of the display apparatusaccording to an exemplary embodiment is substantially similar to the LEDpixel 200 of the display apparatus of FIG. 36, except that a second LEDstack 233 covers most regions of a first LED stack 223, and a third LEDstack 243 covers most regions of the second LED stack 233. Thus, lightgenerated in a first sub-pixel R substantially passes through the secondLED stack 233 and the third LED stack 243, and is emitted to theoutside. In addition, light generated in the second LED stack 233substantially passes through the third LED stack 243 and is emitted tothe outside.

The first LED stack 223 may include an active layer with a narrow bandgap as compared to the second LED stack 233 and the third LED stack 243,and may emit light having a relatively long wavelength than that emittedfrom the second LED stack 233 and the third LED stack 243. The secondLED stack 233 may include an active layer with a narrow band gap ascompared to the third LED stack 243, and may emit light having arelatively long wavelength than that emitted in the third LED stack 243.

FIG. 49 is an enlarged plan view of one pixel of a display apparatusaccording to an exemplary embodiment, and FIGS. 50A and 50B arecross-sectional views taken along lines G-G and H-H of FIG. 49,respectively.

Referring to FIGS. 49, 50A and 50B, the pixel according to an exemplaryembodiment is substantially similar to the pixel described withreference to FIGS. 38, 39A, 39B and 39C, except that a second LED stack233 covers most regions of a first LED stack 223 and a third LED stack243 covers most regions of the second LED stack 233. First through thirdthrough-vias 227 a, 227 b, and 227 c may be disposed outside the secondLED stack 233 and the third LED stack 243.

An upper surface of the first LED stack 223 exposes the through-vias 227a, 227 b, and 227 c as shown in the drawings, however, according to someexemplary embodiments, the through-vias 227 a, 227 b and 227 c may beomitted.

A portion of a first-1 ohmic electrode 229 a and a portion of a second-1ohmic electrode 239 may be disposed under the third LED stack 243. Tothis end, the first-1 ohmic electrode 229 a may be formed before thesecond LED stack 233 is bonded to the first LED stack 223, and thesecond-1 ohmic electrode 239 may also be formed before the third LEDstack 243 is bonded to the second LED stack 233.

Light generated in the first LED stack 223 substantially passes throughthe second LED stack 233 and the third LED stack 243, and is emitted tothe outside. Light generated in the second LED stack 233 substantiallypasses through the third LED stack 243 and is emitted to the outside.Thus, a first bonding layer 253 and a second bonding layer 255 may beformed of light-transmissive materials, and a second-2 ohmic electrode235 and a third-2 ohmic electrode 245 may be formed of transparentconductive layers.

An indented part is formed in the third LED stack 243 to expose thethird-2 ohmic electrode 245, and an indented part is continuously formedin the third LED stack 243 and the second LED stack 233 to expose thesecond-2 ohmic electrode 235. The second-2 ohmic electrode 235 and thethird-2 ohmic electrode 245 are electrically connected to the secondthrough-via 227 b and the third through-via 227 c through connectors 272and 273, respectively.

In addition, since the indented part is formed in the third LED stack243, the second-1 ohmic electrode 239 formed on the first conductivitytype semiconductor layer 233 a of the second LED stack 233 may beexposed. Also, since the indented part is continuously formed in thethird LED stack 243 and the second LED stack 233, the first-1 ohmicelectrode 229 a formed on the first conductivity type semiconductorlayer 223 a of the first LED stack 223 may be exposed. The connector 271may connect the first-1 ohmic electrode 229 a and the second-1 ohmicelectrode 239 to the third-1 ohmic electrode 249. The third-1 ohmicelectrode 249 may be formed together with the connector 271, and may beconnected to a pad region of each of the first-1 ohmic electrode 229 aand the second-1 ohmic electrode 239.

A portion of the first-1 ohmic electrode 229 a and a portion of thesecond-1 ohmic electrode 239 are disposed under the third LED stack 243,but the inventive concepts are not limited thereto. The portion of thefirst-1 ohmic electrode 229 a and the portion of the second-1 ohmicelectrode 239 disposed under the third LED stack 243 may be omitted. Inaddition, the second-1 ohmic electrode 239 may be omitted, and theconnector 271 may be in ohmic contact with the first conductivity typesemiconductor layer 233 a.

As in the above-described exemplary embodiment, the third LED stack 243,the second bonding layer 255, the second LED stack 233, and the firstbonding layer 253 include inclined side surfaces, connectors 271 and 273are formed on the inclined side surfaces, and connector 272 is formed onthe included side surface of the first bonding layer 253.

According to the exemplary embodiments, a plurality of pixels may beformed at a wafer level using wafer bonding, and thus, the step ofindividually mountings LEDs may be obviated.

In addition, since the through-vias 227 a, 227 b, and 227 c are formedin the substrate 221 and are used as current paths, it is not necessaryto remove the substrate 221. Thus, a growth substrate used to grow thefirst LED stack 223 may be used as the substrate 221 without removingthe growth substrate from the first LED stack 223. However, theinventive concepts are not limited thereto, and the substrate 221 may beremoved from the first LED stack 223, and the first LED stack 223 may bebonded to the circuit board 251 using a bonding layer. Here, theconnectors 271, 272, and 273 may be connected directly to the circuitboard 251. To this end, the first LED stack 223 and the bonding layermay be formed to have inclined side surfaces.

Furthermore, the first LED stack 223, the second LED stack 233, and thethird LED stack 243 are stacked in a vertical direction, andaccordingly, when the first through third LED stacks 223, 233, and 243and the first and second bonding layers 253 and 255 have vertical sidesurfaces, it may be difficult to securely form the connectors 271, 272and 273 on the vertical side surfaces. According to exemplaryembodiments, a side surface on which wiring, such as the connectors 271,272 and 273, is to be formed among side surfaces of the first throughthird LED stacks 223, 233, and 243, and the first and second bondinglayers 253 and 255 may be inclined, so that the wiring may be securelyformed. Thus, it is possible to enhance reliability of the displayapparatus.

FIG. 51 is a schematic plan view of a display apparatus according to anexemplary embodiment.

Referring to FIG. 51, the display apparatus includes a circuit board 401and a plurality of light emitting devices 400.

The circuit board 401 may include a circuit for passive matrix drivingor active matrix driving. In one exemplary embodiment, the circuit board401 may include interconnection lines and resistors therein. In anotherexemplary embodiment, the circuit board 401 may include interconnectionlines, transistors, and capacitors. The circuit board 401 may also havepads on the upper surface such that the circuit disposed therein can beelectrically connected to external components.

A plurality of light emitting devices 400 are arranged on the circuitboard 401. Each light emitting device 400 may constitute one pixel. Thelight emitting device 400 has electrode pads 481 a, 481 b, 481 c, and481 d electrically connected to the circuit board 401. The lightemitting device 400 may also include a substrate 441 on the uppersurface thereof. Since the light emitting devices 400 are spaced apartfrom each other, the substrates 441 disposed on the upper surfaces ofthe light emitting devices 400 are also spaced apart from each other.

The configuration of the light emitting device 400 will be described indetail with reference to FIGS. 52A, 52B, and 52C. FIG. 52A is aschematic plan view of the light emitting device 400 according to anexemplary embodiment, FIG. 52B is a cross-sectional view taken alongline A-A of FIG. 52A, and FIG. 52C is a cross-sectional view taken alongline B-B of FIG. 52A. Although it is shown and described herein that theelectrode pads 481 a, 481 b, 481 c, and 481 d are arranged on the upperside, however, the inventive concepts are not limited thereto, and thelight emitting device 400 according to some exemplary embodiments may beflip-bonded on the circuit board 401 of FIG. 51, and in this case, theelectrode pads 481 a, 481 b, 481 c, and 481 d may be arranged on thelower side of the light emitting device 400.

Referring to FIGS. 52A, 52B and 52C, the light emitting device 400includes the substrate 441, the electrode pads 481 a, 481 b, 481 c, and481 d, a first LED stack 423, a second LED stack 433, a third LED stack443, a first transparent electrode 425, a second transparent electrode435, a third transparent electrode 445, an ohmic electrode 427, a firstcolor filter 447, a second color filter 457, a first bonding layer 449,a second bonding layer 459, and an insulating layer 461.

The substrate 441 may support the semiconductor stacks 423, 433, and443. In addition, the substrate 441 may be a growth substrate forgrowing the third LED stack 443. For example, the substrate 441 may be asapphire substrate or a gallium nitride substrate, in particular, apatterned sapphire substrate. The LED stacks are disposed on thesubstrate 441 in the order of the third LED stack 443, the second LEDstack 433, and the first LED stack 423.

In an exemplary embodiment, a single third LED stack may be disposed onone substrate 441, and thus, the light emitting device 400 may have asingle-chip structure of a single pixel. According to another exemplaryembodiment, the substrate 441 may be omitted and the lower surface ofthe third LED stack 443 may be exposed. In this case, a roughenedsurface may be formed on the lower surface of the third LED stack 443 bysurface texturing.

According to still another exemplary embodiment, a plurality of thirdLED stacks 443 may be disposed on one substrate 441, and the second LEDstack 433 and the first LED stack 423 may be disposed on each third LEDstack 443. Accordingly, the light emitting device 400 may include aplurality of pixels.

The first LED stack 423, the second LED stack 433, and the third LEDstack 443 each include a first conductivity type semiconductor layer 423a, 433 b or 443 a, a second conductivity type semiconductor layer 423 b,433 b or 443 b, and an active layer interposed therebetween. The activelayer may have a multiple quantum well structure.

For the LED stacks 423, 433, and 443, the closer to the substrate 441the LED stack is, the shorter wavelength light may be emitted from theLED stack. For example, the first LED stack 423 may be an inorganiclight emitting diode emitting red light, the second LED stack 433 may bean inorganic light emitting diode emitting green light, and the thirdLED stack 443 may be an inorganic light emitting diode emitting bluelight. The first LED stack 423 may include AlGaInP based semiconductorlayers, the second LED stack 433 may include AlGaInP based or AlGaInNbased semiconductor layers, and the third LED stack 443 may includeAlGaInN based semiconductor layers. However, the inventive concepts arenot limited thereto, and when LED stacks include micro LEDs, the LEDstack disposed closest to the substrate 440 may emit light having thelongest wavelength, or light having an intermediate wavelength than theLED stack disposed thereabove, without adversely affecting the operationand without requiring color filters due to small form factor of a microLED.

The first conductivity type semiconductor layers 423 a, 433 a, and 443 aof the respective LED stacks 423, 433, and 443 may be n-typesemiconductor layers and the second conductivity type semiconductorlayers 423 b, 433 b, and 443 b of the respective LED stacks 423, 433,and 443 may be p-type semiconductor layers. In particular, the uppersurface of the first LED stack 423 may be an n-type semiconductor layer423 a, the upper surface of the second LED stack 433 may be an n-typesemiconductor layer 433 a, and the upper surface of the third LED stack443 may be a p-type semiconductor layer 443 b. That is, the order of thesemiconductor layers is reversed only in the third LED stack 443.Accordingly, the p-type semiconductor layers of the second LED stack 433and the third LED stack 443 are arranged to face each other. However,the inventive concepts are not limited thereto, and the p-typesemiconductor layer 423 b of the first LED stack 423 and the p-typesemiconductor layer 433 b of the second LED stack 433 may be arranged toface each other. Further, the n-type semiconductor layer 433 a of thesecond LED stack 433 and the n-type semiconductor layer 443 a of thethird LED stack 443 may be arranged to face each other, or the n-typesemiconductor layer 423 a of the first LED stack 423 and the n-typesemiconductor layer 433 a of the second LED stack 433 may be arranged toface each other.

In the first LED stack 423, the first conductivity type semiconductorlayer 423 a may have substantially the same area as the secondconductivity type semiconductor layer 423 b, and thus, the firstconductivity type semiconductor layer 423 a and the second conductivitytype semiconductor layer 423 b may overlap with each other. Also in thesecond LED stack 433, the first conductivity type semiconductor layer433 a may have substantially the same area as the second conductivitytype semiconductor layer 433 b, and thus, the first conductivity typesemiconductor layer 433 a and the second conductivity type semiconductorlayer 433 b may overlap with each other. In the third LED stack 443, thesecond conductivity type semiconductor layer 443 b may be disposed on apartial region of the first conductivity type semiconductor layer 443 a,and thus, the first conductivity type semiconductor layer 443 a ispartially exposed.

The first LED stack 423 and the second LED stack 433 may be disposed ona partial region of the third LED stack 443. Furthermore, the first andsecond LED stacks 423 and 433 may be disposed in the upper region of thesecond conductivity type semiconductor layer 443 b. More specifically,the second LED stack 433 may be disposed on a partial region of thesecond conductivity type semiconductor layer 443 b, and the first LEDstack 423 may be disposed on a partial region of the second LED stack433. The second LED stack 433 may include a region disposed outside thefirst LED stack 423, and the third LED stack 443 may include a regiondisposed outside the second LED stack 433.

The first LED stack 423 is disposed farther away from the substrate 441,the second LED stack 433 is disposed below the first LED stack 423, andthe third LED stack 443 is disposed below the second LED stack 433. Thefirst LED stack 423 emits light having a longer wavelength than thesecond and third LED stacks 433 and 443, so that light generated in thefirst LED stack 423 may be emitted to the outside through the second andthird LED stacks 433 and 443 and the substrate 441. In addition, thesecond LED stack 433 emits light having a longer wavelength than thethird LED stack 443, so that light generated in the second LED stack 433may be emitted to the outside through the third LED stack 443 and thesubstrate 441. However, the inventive concepts are not limited thereto,and when LED stacks include micro LEDs, the LED stack disposed closestto the substrate 440 may emit light having the longest wavelength, orlight having an intermediate wavelength than the LED stack disposedthereabove, without adversely affecting the operation or requiring colorfilters due to small form factor of a micro LED.

The first transparent electrode 425 is in ohmic contact with the secondconductivity type semiconductor layer 423 b of the first LED stack 423and transmits light generated in the first LED stack 423. The firsttransparent electrode 425 may be formed of a metal layer or a conductiveoxide layer which is transparent to red light.

As shown in FIG. 52B, the first transparent electrode 425 may include aportion protruding outside the first LED stack 423. That is, the firsttransparent electrode 425 may include a region exposed outside the firstLED stack 423.

The ohmic electrode 427 is in ohmic contact with the first conductivitytype semiconductor layer 423 a of the first LED stack 423. In oneexemplary embodiment, the ohmic electrode 427 may include a reflectivemetal layer, and thus may reflect light generated in the first LED stack423 toward the substrate 441. The ohmic electrode 427 may be formed of,for example, AuTe, AuGe, or others. In another exemplary embodiment, theohmic electrode 427 may be formed of a material layer transparent to redlight, such as a conductive oxide layer.

The ohmic electrode 427 may cover most of the region of the first LEDstack 423, but is not limited thereto, and may be partially in contactwith the first conductivity type semiconductor layer 423 a.

The second transparent electrode 435 in ohmic contact with the secondconductivity type semiconductor layer 433 b of the second LED stack 433.As shown in the drawing, the second transparent electrode 435 is incontact with the lower surface of the second LED stack 433 between thesecond LED stack 433 and the third LED stack 443. In addition, as shownin FIG. 52B, the second transparent electrode 435 may include a regionprotruding outside the second LED stack 433. That is, the secondtransparent electrode 435 may include a region exposed outside thesecond LED stack 433. The second transparent electrode 435 may be formedof a metal layer or a conductive oxide layer which is transparent to redlight and green light.

The third transparent electrode 445 is in ohmic contact with the secondconductivity type semiconductor layer 443 b of the third LED stack 433.The third transparent electrode 445 may be disposed between the secondLED stack 433 and the third LED stack 443 and is in contact with theupper surface of the third LED stack 443. The third transparentelectrode 445 may be formed of a metal layer or a conductive oxide layerwhich is transparent to red light and green light. The third transparentelectrode 445 may also be transparent to blue light. The thirdtransparent electrode 445 is disposed in the upper region of the secondconductivity type semiconductor layer 443 b and therefore has a narrowerarea than the first conductivity type semiconductor layer 443 a.

The first transparent electrode 425, the second transparent electrode435, and the third transparent electrode 445 may assist currentspreading by being in ohmic contact with the p-type semiconductor layerof each LED stack. Examples of the conductive oxide layer used for thefirst, second, and third transparent electrodes 425, 435, and 445include SnO₂, InO₂, ITO, ZnO, IZO, or others. In addition, the first,second, and third transparent electrodes 425, 435, and 445 may be usedas an etch stop layer, and the exposed portion and unexposed portion mayhave different thicknesses.

The first color filter 447 may be disposed between the third transparentelectrode 445 and the second LED stack 433, and the second color filter457 may be disposed between the second LED stack 433 and the first LEDstack 423. The first color filter 447 transmits light generated in thefirst and second LED stacks 423 and 433 and reflects light generated inthe third LED stack 443. The second color filter 457 transmits lightgenerated in the first LED stack 423 and reflects light generated in thesecond LED stack 433. Accordingly, light generated in the first LEDstack 423 can be emitted to the outside through the second LED stack 433and the third LED stack 443, and light generated in the second LED stack433 can be emitted to the outside through the third LED stack 443.Furthermore, light generated in the second LED stack 433 may beprevented from being lost by being incident on the first LED stack 423,or light generated in the third LED stack 443 may be prevented frombeing lost by being incident on the second LED stack 433.

In some exemplary embodiments, the second color filter 457 may reflectlight generated in the third LED stack 443.

The first and second color filters 447 and 457 are, for example, a lowpass filter that passes a low frequency range, that is, only a longwavelength band, a band pass filter that passes only a predeterminedwavelength band, or a band stop filter that blocks only a predeterminedwavelength band. In particular, the first and second color filters 447and 457 may be formed by alternately stacking insulating layers havingrefractive indices different from each other, for example, may be formedby alternately stacking the TiO₂ insulating layer and the SiO₂insulating layer. In particular, the first and second color filters 447and 457 may include a distributed Bragg reflector (DBR). The stop bandof the distributed Bragg reflector can be controlled by adjusting thethickness of TiO₂ and SiO₂. The low pass filter and the band pass filtermay also be formed by alternately stacking insulating layers havingrefractive indices different from each other.

The first bonding layer 449 adjoins the second LED stack 433 to thethird LED stack 443. The first bonding layer 449 substantially coversthe first color filter 447 and may be bonded to the second transparentelectrode 435. For example, the first bonding layer 449 may be atransparent organic layer or a transparent inorganic layer. Examples ofthe organic layer include SU8, poly(methylmethacrylate) (PMMA),polyimide, parylene, and benzocyclobutene (BCB), examples of theinorganic layer include Al₂O₃, SiO₂, SiN_(x), or others. The firstbonding layer 449 may also be formed of spin-on-glass (SOG). The organiclayers may be bonded at a high vacuum and a high pressure, and theinorganic layers may be bonded under a high vacuum in a state in whichthe surface energy is changed by using plasma or others, afterplanarizing the surface by a chemical mechanical polishing process, forexample.

The second bonding layer 459 couples the second LED stack 433 to thefirst LED stack 423. As shown in the drawing, the second bonding layer459 may cover the second color filter 457 and be in contact with thefirst transparent electrode 425. The second bonding layer 459 may beformed of substantially the same material as the first bonding layer 449described above.

The insulating layer 461 covers the side surfaces and upper region ofthe first, second, and third LED stacks 423, 433, and 443. In oneexemplary embodiment, the insulating layer 461 may be formed of a lighttransmitting material SiO₂, Si₃N₄, or SOG. In another exemplaryembodiment, the insulating layer 461 may contain a light reflectinglayer or a light blocking layer, such as a light absorbing layer, toprevent optical interference with the adjacent light emitting device.For example, the insulating layer 461 may include a distributed Braggreflector that reflects red light, green light, and blue light, or anSiO₂ layer with a reflective metallic layer or a highly reflectiveorganic layer deposited thereon. Alternatively, the insulating layer 461may contain an absorbing layer, such as a black epoxy, for lightblocking. The light blocking layer may increase the contrast ratio of animage by preventing optical interference between the light emittingdevices.

The insulating layer 461 may have openings 461 a, 461 b, 461 c, 461 d,and 461 e for electrical paths. For example, the insulating layer 461includes the openings 461 a, 461 b, 461 c, 461 d, and 461 e for exposingthe ohmic electrode 427, the first transparent electrode 425, the secondand third transparent electrodes 435 and 445, and the second and thirdLED stacks 433 and 443. The opening 461 a exposes the ohmic electrode427, the opening 461 b exposes the first conductivity type semiconductorlayer 433 a of the second LED stack 433, and the opening 461 c exposesthe first conductivity type semiconductor layer 443 a of the third LEDstack 443. The opening 461 d exposes the first transparent electrode 425and the opening 461 e exposes the second transparent electrode 435 andthe third transparent electrode 445 together. In another exemplaryembodiment, the second transparent electrode 435 and the thirdtransparent electrode 445 may be exposed by different openings. However,when the second and third transparent electrodes 435 and 445 are exposedby one opening 461 e, the second and third transparent electrodes 435and 445 may be exposed to a relatively great extent.

The electrode pads 481 a, 481 b, 481 c, and 481 d are disposed over thefirst LED stack 423, and are electrically connected to the first,second, and third LED stacks 423, 433, and 443. The electrode pads 481a, 481 b, 481 c, and 481 d may include the first, second, and thirdelectrode pads 481 a, 481 b, and 481 c and the common electrode pad. Theelectrode pads 481 a, 481 b, 481 c, and 481 d may be disposed on theinsulating layer 461, and be connected to the ohmic electrode 427exposed by the openings 461 a, 461 b, 461 c, 461 d, and 461 e of theinsulating to layer 461, the first, second, and third transparentelectrodes 425, 435 and 445, and the first conductivity typesemiconductor layers 433 a and 443 a of the second and third LED stacks.For example, the first electrode pad 481 a may be connected to the ohmicelectrode 427 through the opening 461 a. The first electrode pad 481 ais electrically connected to the first conductivity type semiconductorlayer 423 a of the first LED stack 423 through the ohmic electrode 427.

In addition, the second electrode pad 481 b may be connected to thefirst conductivity type semiconductor layer 433 a of the second LEDstack 433 through the opening 461 b of the insulating layer 461, and thethird electrode pad 481 c may be electrically connected to the firstconductivity type semiconductor layer 443 a of the third LED stack 443through the opening 461 c of the insulating layer 461.

The common electrode pad 481 d may be connected in common to the firsttransparent electrode 425, the second transparent electrode 435, and thethird transparent electrode 445 through the openings 461 d and 461 e.Accordingly, the common electrode pad 481 d is electrically connected incommon to the second conductivity type semiconductor layer 423 b of thefirst LED stack 423, the second conductivity type semiconductor layer433 b of the second LED stack 433, and the second conductivity typesemiconductor layer 443 b of the third LED stack 443.

According to an exemplary embodiment, the first LED stack 423 iselectrically connected to the electrode pads 481 d and 481 a, and thesecond LED stack 433 is electrically connected to the electrode pads 481d and 481 b, and the third LED stack 443 is electrically connected tothe electrode pads 481 d and 481 c. Accordingly, anodes of the first LEDstack 423, the second LED stack 433, and the third LED stack 443 areelectrically connected in common to the electrode pad 481 d, andcathodes thereof are electrically connected to the first, second, andthird electrode pads 481 a, 481 b, and 481 c, respectively. Thus, thefirst, second, and third LED stacks 423, 433, and 443 can beindependently driven.

While the first, second, and third electrode pads 481 a, 481 b, and 481c are described as being electrically connected to the firstconductivity type semiconductor layers 423 a, 433 a, and 443 a and thecommon electrode pad 481 d is described as being electrically connectedto the second conductivity type semiconductor layers 423 b, 433 b, and443 b, the inventive concepts are not limited thereto. For example, thefirst, second, and third electrode pads 481 a, 481 b, and 481 c may beelectrically connected to the second conductivity type semiconductorlayers 423 b, 433 b, 443 b, and the common electrode pad 481 d may beelectrically connected to the first conductivity type semiconductorlayers 423 a, 433 a, and 443 a.

FIGS. 53, 54, 55, 56, 57A, 57B, 58A, 58B, 59A, 59B, 60A, 60B, 61A, 61B,62A, 62B, 63A, 63B, 64A, and 64B are schematic plan views andcross-sectional views illustrating a method of manufacturing the lightemitting device 400 according to an exemplary embodiment. In thedrawings, each plan view corresponds to a plan view of FIG. 52A, andeach cross-sectional view corresponds to a cross-sectional view takenalong line A-A of FIG. 52A.

Referring to FIG. 53, the first LED stack 423 is grown on a firstsubstrate 421. The first substrate 421 may be a GaAs substrate, forexample. The first LED stack 423 is formed of AlGaInP basedsemiconductor layers, and includes the first conductivity typesemiconductor layer 423 a, the active layer, and the second conductivitytype semiconductor layer 423 b. Here, the first conductivity type may ben-type and the second conductivity type may be p-type.

The first transparent electrode 425 may be formed on the first LED stack423. The first transparent electrode 425 may be formed of a conductiveoxide layer such as SnO₂, InO₂, ITO, ZnO, IZO, or others.

Referring to FIG. 54, the second LED stack 433 is grown on a secondsubstrate 31, and the second transparent electrode 435 is formed on thesecond LED stack 433. The second LED stack 433 is AlGaInP based orAlGaInN based semiconductor layers, and may include the firstconductivity type semiconductor layer 433 a, the active layer, and thesecond conductivity type semiconductor layer 433 b. The active layer mayinclude an AlGaInP based or AlGaInN well layer. Here, the firstconductivity type may be n-type and the second conductivity type may bep-type.

The second substrate 31 may be a substrate on which an AlGaInP basedsemiconductor layer can be grown, for example, a GaAs substrate, or asubstrate on which an AlGaInN based semiconductor layer can be grown,for example, a GaN substrate or a sapphire substrate. The compositionratio of the well layer can be determined so that the second LED stack433 emits green light. The second transparent electrode 435 is in ohmiccontact with the second conductivity type semiconductor layer 433 b. Thesecond transparent electrode 435 may be formed of a conductive oxidelayer such as SnO₂, InO₂, ITO, ZnO, IZO, or others.

Referring to FIG. 55, the third LED stack 443 is grown on a thirdsubstrate 441, and the third transparent electrode 445 and the firstcolor filter 447 are formed on the third LED stack 443. The third LEDstack 443 is formed of AlGaInN based semiconductor layers, and mayinclude the first conductivity type semiconductor layer 443 a, theactive layer, and the second conductivity type semiconductor layer 443b. The active layer may also include an AlGaInN based well layer. Here,the first conductivity type may be n-type and the second conductivitytype may be p-type.

The third substrate 441 is a substrate on which a gallium nitride basedsemiconductor layer can be grown, and may be a sapphire substrate or aGaN substrate. The composition ratio of the AlGaInN can be determined sothat the third LED stack 443 emits blue light. The third transparentelectrode 445 is in ohmic contact with the second conductivity typesemiconductor layer 443 b. The third transparent electrode 445 may beformed of a conductive oxide layer such as SnO₂, InO₂, ITO, ZnO, IZO, orothers.

Since the first color filter 447 substantially the same as thatdescribed with reference to FIGS. 52A, 52B, and 52C, detaileddescriptions thereof will be omitted in order to avoid redundancy.

Referring to FIG. 56, the second LED stack 433 described with referenceto FIG. 54 is bonded onto the third LED stack 443 of FIG. 55.

The first color filter 447 and the second transparent electrode 435 arebonded so as to face each other. For example, bonding material layersare formed on the first color filter 447 and the second transparentelectrode 435, respectively, and by bonding the first color filter 447and the second transparent electrode 435, the first bonding layer 449may be formed. The bonding material layers may be, for example, atransparent organic layer or a transparent inorganic layer. Examples ofthe organic layer include SU8, poly(methylmethacrylate) (PMMA),polyimide, parylene, benzocyclobutene (BCB), or others, and examples ofthe inorganic layer include Al₂O₃, SiO₂, SiN_(x), or others. Inaddition, the first bonding layer 449 may be formed using spin-on-glass(SOG).

Then, the second substrate 31 is removed from the second LED stack 433using techniques such as laser lift-off, chemical lift-off, or others.Accordingly, the first conductivity type semiconductor layer 433 a ofthe second LED stack 433 is exposed from above. A surface roughened bysurface texturing may be formed on the surface of the exposed firstconductivity type semiconductor layer 433 a.

Then, the second color filter 457 is formed on the exposed firstconductivity type semiconductor layer 433 a of the second LED stack 433.Since the second color filter 457 is substantially the same as thatdescribed with reference to FIGS. 52A, 52B, and 52C, detaileddescriptions thereof will be omitted to avoid redundancy.

The first LED stack 423 of FIG. 53 is bonded on the second LED stack433. The second color filter 457 and the first transparent electrode 425may be bonded to face each other. For example, bonding material layersare formed on the second color filter 457 and the first transparentelectrode 425, respectively, and by bonding the second color filter 457and the first transparent electrode 425, the second bonding layer 459may be formed. The bonding material layers may be, for example, atransparent organic layer or a transparent inorganic layer as describedabove.

Then, the first substrate 421 is removed from the first LED stack 423.The first substrate 421 may be removed using, for example, a wet etchingtechnique. Accordingly, the first conductivity type semiconductor layer423 a is exposed. The surface of the exposed first conductivity typesemiconductor layer 423 a may be textured to improve light extractionefficiency, which makes it possible to form a roughened surface or alight extracting structure on the surface of the first conductivity typesemiconductor layer 423 a.

Referring to FIGS. 57A and 57B, the first LED stack 423 is patterned toexpose the first transparent electrode 425. Although the drawings showone light emitting device region, the first LED stack 423 is patternedin a plurality of light emitting device regions on the substrate 441,and the first transparent electrode 425 is exposed. The firsttransparent electrode 425 may be used as an etch stop layer when thefirst LED stack 423 is patterned, which makes it possible etch a part ofthe first transparent electrode 425 exposed to the outside of the firstLED stack 423 to form a step on the first transparent electrode 425.That is, the first transparent electrode 425 below the first LED stack423 may be thicker than the first transparent electrode 425 outside thefirst LED stack 423.

Referring to FIGS. 58A and 58B, subsequently, the first transparentelectrode 425, the second bonding layer 459, and the second color filter457 are patterned such that the first conductivity type semiconductorlayer 433 a of the second LED stack 433 is exposed. As shown in FIG.58A, the first transparent electrode 425 is patterned such that a partof the first transparent electrode 425 remains outside the first LEDstack 423 in a plan view.

Referring to FIGS. 59A and 59B, the first and second conductivity typesemiconductor layers 433 a and 433 b are patterned to expose the secondtransparent electrode 435. As shown in FIG. 59A, the first conductivitytype semiconductor layer 433 a is patterned such that a part of thefirst conductivity type semiconductor layer 433 a remains outside thefirst LED stack 423 in a plan view. The second transparent electrode 435may be used as an etch stop layer during the patterning of the first andsecond conductivity type semiconductor layers 433 a and 433 b.Accordingly, in the second transparent electrode 435, a part disposedoutside the second LED stack 433 may be thinner than a part disposedbelow the second LED stack 433 so that a step is formed.

Referring to FIGS. 60A and 60B, the second transparent electrode 435,the first bonding layer 449, and the first color filter 447 aresequentially patterned to expose the third transparent electrode 445.The third transparent electrode 445 may be used as an etch stop layer,so that a step may also be formed on the third transparent electrode445. That is, in the third transparent electrode 445, a part exposedoutside the first color filter 447 may be relatively thin, compared witha part disposed below the first color filter 447.

As shown in FIG. 58A, the second transparent electrode 435 is patternedsuch that a part of the second transparent electrode 435 remains outsidethe second LED stack 433 in a plan view. The exposed second transparentelectrode 435 is disposed adjacent to the exposed first transparentelectrode 425.

Referring to FIGS. 61A and 61B, the third transparent electrode 445 andthe second conductivity type semiconductor layer 443 a are patterned toexpose the first conductivity type semiconductor layer 443 a.

A part of the third transparent electrode 445 is exposed to the outsideof the second LED stack 433 to be viewed in a plan view. The exposedthird transparent electrode 445 is disposed adjacent to the exposedsecond transparent electrode 435.

Referring to FIGS. 62A and 62B, the ohmic electrode 427 is formed on thefirst conductivity type semiconductor layer 423 a of the first LED stack423. The ohmic electrode 427 is in ohmic contact with the firstconductivity type semiconductor layer 423 a and may be formed of a metallayer, such as AuTe or AuGe.

Referring to FIGS. 63A and 63B, the insulating layer 461 covering thefirst, second, and third LED stacks 423, 433, and 443 is formed. Theinsulating layer 461 may be formed as a single layer or multiple layersof SiO₂, Si₃N₄, SOG, or others. Alternatively, the insulating layer 461may include a light reflecting layer or a light absorbing layer to avoidoptical interference with the adjacent light emitting device. Forexample, the insulating layer 461 may include a distributed Braggreflector that reflects red light, green light, and blue light, or alayer of SiO₂ with a reflective metallic layer or a highly reflectiveorganic layer deposited thereon. Alternatively, the insulating layer 461may include, for example, black epoxy as a light absorbing material. Thelight reflecting layer or the light absorbing layer prevents opticalinterference between the light emitting devices, which results inincrease in the contrast ratio of the image.

The insulating layer 461 may cover the upper surface and side surfacesof the first, second, and third LED stacks 423, 433, and 443. Theinsulating layer 461 also covers the exposed first, second, and thirdtransparent electrodes 425, 435, and 445. The insulating layer 461 mayalso cover the ohmic electrode 427.

The insulating layer 461 is patterned to include the openings 461 a, 461b, 461 b, 461 c, 461 d, and 461 e for exposing the ohmic electrode 427,the first conductivity type semiconductor layers 433 a and 443 a, andthe first, second, and third transparent electrodes 425, 435, and 445.In particular, the opening 461 e may expose the second transparentelectrode 435 and the third transparent electrode 445 together.

Although the ohmic electrode 427, the first conductivity typesemiconductor layer 433 a, and the first conductivity type semiconductorlayer 443 a are each shown and described as being exposed by oneopening, each of them may be exposed by a plurality of openings. Inaddition, the second and third transparent electrodes 435 and 445 may beexposed by different openings, respectively, and the first, second, andthird transparent electrodes 425, 435, and 445 each may be exposed by aplurality of openings.

Referring to FIGS. 64A and 64B, the electrode pads 481 a, 481 b, 481 c,and 481 d are formed on the insulating layer 461. The electrode pads 481a, 481 b, 481 c, and 481 d include the first electrode pad 481 a, thesecond electrode pad 481 b, the third electrode pad 481 c, and thecommon electrode pad 481 d.

The common electrode pad 481 d is connected to the first transparentelectrode 425, the second transparent electrode 435, and the thirdtransparent electrode 445 through the openings 461 d and 461 e. Thus,the common electrode pad 481 d is electrically connected in common tothe anodes of the first, second, and third LED stacks 423, 433, and 443.In particular, the common electrode pad 481 d may be simultaneouslyconnected to the second transparent electrode 435 and the thirdtransparent electrode 445 through one opening 461 e.

The first electrode pad 481 a is connected to the ohmic electrode 427and electrically connected to the cathode of the first LED stack 423,that is, the first conductivity type semiconductor layer 423 a throughthe opening 461 a. The second electrode pad 481 b is electricallyconnected to the cathode of the second LED stack 433, that is, the firstconductivity type semiconductor layer 433 a through the opening 461 b,and the third electrode pad 481 c is electrically connected to thecathode of the third LED stack 443, that is, the first conductivity typesemiconductor layer 443 a through the opening 461 c.

The electrode pads 481 a, 481 b, 481 c, and 481 d are electricallyseparated from each other, so that each of the first, second, and thirdLED stacks 423, 433, and 443 is electrically connected to two electrodepads, and is adapted to be independently driven.

Subsequently, the light emitting device 400 of FIG. 52A according to anexemplary embodiment is provided by dividing the substrate 441 intolight emitting device regions.

As shown in FIG. 64A, the electrode pads 481 a, 481 b, 481 c, and 481 dmay be disposed at four corners of each light emitting device 400. Inaddition, the electrode pads 481 a, 481 b, 481 c, and 481 d may havesubstantially a rectangular shape, but the inventive concepts are notlimited thereto.

Further, although the substrate 441 is described as being divided, thesubstrate 441 may be removed so that the surface of the exposed firstconductivity type semiconductor layer 443 may be textured.

A light emitting device according to an exemplary embodiment has astructure, in which anodes of the first, second, and third LED stacks423, 433, and 443 are electrically connected in common, and cathodesthereof are independently connected. However, the inventive concepts arenot limited thereto, and the anodes of the first, second, and third LEDstacks 423, 433, and 443 may be independently connected to the electrodepads, and the cathodes may be electrically connected to the commonelectrode pad in common.

The light emitting device 400 may include the first, second, and thirdLED stacks 423, 433, and 443 to emit red, green, and blue light, andthus may be used as a single pixel in a display apparatus. As describedwith reference to FIG. 51, a display apparatus may be provided byarranging a plurality of light emitting devices 400 on the circuit board401. Since the light emitting device 400 includes the first, second, andthird LED stacks 423, 433, and 443, the area of the subpixel in onepixel may be increased. Further, the first, second, and third LED stacks423, 433, and 443 may be mounted by mounting one light emitting device400, thereby reducing the number of mounting processes.

According to the illustrated embodiment, the second transparentelectrode 435 and the third transparent electrode 445 may be exposedtogether through one opening 461 e, and the common electrode pad 481 dmay be connected to the second transparent electrode 435 and the thirdtransparent electrode 445 in common through the opening 461 e. Since thesemiconductor layers of the same conductivity type of the second LEDstack 433 and the third LED stack 443 are disposed to face each other,short circuit may not occur by the common electrode pad 481 d. Thesemiconductor layers of the second conductivity type semiconductorlayers 433 b and 443 b of the second LED stack 433 and the third LEDstack 443 are described as being disposed to face each other, but theinventive concepts are not limited thereto.

As described with reference to FIG. 51, the light emitting devices 400mounted on the circuit board 401 may be driven by a passive matrixmethod or an active matrix method.

FIG. 65 is a schematic cross-sectional view of a light emitting diode(LED) stack for a display according to an exemplary embodiment.

Referring to FIG. 65, the light emitting diode stack 4000 for a displaymay include a support substrate 4051, a first LED stack 4023, a secondLED stack 4033, a third LED stack 4043, a reflective electrode 4025, anohmic electrode 4026, a first insulating layer 4027, a second insulatinglayer 4028, a interconnection line 4029, a second-p transparentelectrode 4035, a third-p transparent electrode 4045, a first colorfilter 4037, a second color filter 4047, hydrophilic material layers4052, 4054, and 4056, a first bonding layer 4053 (a lower bondinglayer), a second bonding layer 4055 (an intermediate bonding layer), anda third bonding layer 4057 (an upper bonding layer).

The support substrate 4051 supports semiconductor stacks 4023, 4033, and4043. The support substrate 4051 may have a circuit on a surface thereofor an inside thereof, but is not limited thereto. The support substrate4051 may include, for example, a glass, a sapphire substrate, a Sisubstrate, or a Ge substrate.

The first LED stack 4023, the second LED stack 4033, and the third LEDstack 4043 each include first conductivity type semiconductor layers4023 a, 4033 a, and 4043 a, second conductivity type semiconductorlayers 4023 b, 4033 b, and 4043 b, and active layers interposed betweenthe first conductivity type semiconductor layers and the secondconductivity type semiconductor layers. The active layer may have amultiple quantum well structure.

The first LED stack 4023 may be an inorganic LED that emits red light,the second LED stack 4033 may be an inorganic LED that emits greenlight, and the third LED stack 4043 may be an inorganic LED that emitsblue light. The first LED stack 4023 may include a GaInP-based welllayer, and the second LED stack 4033 and the third LED stack 4043 mayinclude a GaInN-based well layer. However, the inventive concepts arelimited thereto, and when the LED stacks include micro LEDs, the firstLED stack 4023 may emit any one of red, green, and blue light, and thesecond and third LED stacks 4033 and 4043 may emit a different one ofthe red, green, and blue light without adversely affecting operation orrequiring color filters due to its small form factor.

Opposite surfaces of each LED stack 4023, 4033, or 4043 are an n-typesemiconductor layer and a p-type semiconductor layer, respectively. Theillustrated exemplary embodiment describes a case in which the firstconductivity type semiconductor layers 4023 a, 4033 a, and 4043 a ofeach of the first to third LED stacks 4023, 4033, and 4043 are n-type,and the second conductivity type semiconductor layers 4023 b, 4033 b,and 4043 b thereof are p-type. A roughened surface may be formed onupper surfaces of the first to third LED stacks 4023, 4033, and 4043.However, the inventive concepts are not limited thereto, and the type ofthe semiconductor types of the upper surface and the lower surface ofeach of the LED stacks may be reversed.

The first LED stack 4023 is disposed to be adjacent to the supportsubstrate 4051, the second LED stack 4033 is disposed on the first LEDstack 4023, and the third LED stack 4043 is disposed on the second LEDstack 4033. Since the first LED stack 4023 emits light of the wavelengthlonger than the wavelengths of the second and third LED stacks 4033 and4043, light generated in the first LED stack 4023 may be transmittedthrough the second and third LED stacks 4033 and 4043 and may be emittedto the outside. In addition, since the second LED stack 4033 emits lightof the wavelength longer than the wavelength of the third LED stack4043, light generated in the second LED stack 4033 may be transmittedthrough the third LED stack 4043 and may be emitted to the outside.

The reflective electrode 4025 is in ohmic contact with the secondconductivity type semiconductor layer of the first LED stack 4023 andreflects light generated in the first LED stack 4023. For example, thereflective electrode 4025 may include an ohmic contact layer 4025 a anda reflective layer 4025 b.

The ohmic contact layer 4025 a is partially in contact with the secondconductivity type semiconductor layer, that is, a p-type semiconductorlayer. In order to prevent light absorption by the ohmic contact layer4025 a, an area in which the ohmic contact layer 4025 a is in contactwith the p-type semiconductor layer may not exceed about 50% of a totalarea of the p-type semiconductor layer. The reflective layer 4025 bcovers the ohmic contact layer 4025 a and also covers the firstinsulating layer 4027. As illustrated, the reflective layer 4025 b maysubstantially cover the entirety of the ohmic contact layer 4025 a, or aportion of the ohmic contact layer 4025 a.

The reflective layer 4025 b covers the first insulating layer 4027, suchthat an omnidirectional reflector may be formed by a stack of the firstLED stack 4023 having a relatively high refractive index and the firstinsulating layer 4027 and the reflective layer 4025 b having arelatively low refractive index. The reflective layer 4025 b coversabout 50% or more of the area of the first LED stack 4023, preferably,most of the region of the first LED stack 4023, thereby improving lightefficiency.

The ohmic contact layer 4025 a and the reflective layer 4025 b may beformed of a metal layer containing gold (Au). The ohmic contact layer4025 a may be formed of, for example, an Au—Zn alloy or an Au—Be alloy.The reflective layer 4025 b may be formed of a metal layer having highreflectivity with respect to light generated in the first LED stack4023, for example, red light, such as aluminum (Al), silver (Ag), orgold (Au). In particular, Au may have relatively low reflectivity withrespect to light generated in the second LED stack 4033 and the thirdLED stack 4043, for example, green light or blue light, and thus, mayreduce light interference by absorbing light generated in the second andthird LED stacks 4033 and 4043 and traveling toward the supportsubstrate 4051.

The first insulating layer 4027 is disposed between the supportsubstrate 4051 and the first LED stack 4023, and has an opening exposingthe first LED stack 4023. The ohmic contact layer 4025 a is connected tothe first LED stack 4023 within the opening of the first insulatinglayer 4027.

The ohmic electrode 4026 is in ohmic contact with the first conductivitytype semiconductor layer 4023 a of the first LED stack 4023. The ohmicelectrode 4026 may be disposed on the first conductivity typesemiconductor layer 4023 a exposed by partially removing the secondconductivity type semiconductor layer 4023 b. Although FIG. 65illustrates one ohmic electrode 4026, a plurality of ohmic electrodes4026 are aligned on a plurality of regions on the support substrate4051. The ohmic electrode 4026 may be formed of, for example, an Au—Tealloy or an Au—Ge alloy.

The second insulating layer 4028 is disposed between the supportsubstrate 4051 and the reflective electrode 4025 to cover the reflectiveelectrode 4025. The second insulating layer 4028 has an opening exposingthe ohmic electrode 4026. The second insulating layer 4028 may be formedof SiO₂ or SOG.

The interconnection line 4029 is disposed between the second insulatinglayer 4028 and the support substrate 4051, and is connected to the ohmicelectrode 4026 through the opening of the second insulating layer 4028.The interconnection line 4026 may connect a plurality of ohmicelectrodes 4026 to one another on the support substrate 4051.

The second-p transparent electrode 4035 is in ohmic contact with thesecond conductivity type semiconductor layer 4033 b of the second LEDstack 4033, that is, the p-type semiconductor layer. The second-ptransparent electrode 4035 may be formed of a metal layer or aconductive oxide layer which is transparent to red light and greenlight.

The third-p transparent electrode 4045 is in ohmic contact with thesecond conductivity type semiconductor layer 4043 b of the third LEDstack 4043, that is, the p-type semiconductor layer. The third-ptransparent electrode 4045 may be formed of a metal layer or aconductive oxide layer which is transparent to red light, green light,and blue light.

The reflective electrode 4025, the second-p transparent electrode 4035,and the third-p transparent electrode 4045 may be in ohmic contact withthe p-type semiconductor layer of each LED stack to assist in currentdispersion.

The first color filter 4037 may be disposed between the first LED stack4023 and the second LED stack 4033. In addition, the second color filter4047 may be disposed between the second LED stack 4033 and the third LEDstack 4043. The first color filter 4037 transmits light generated in thefirst LED stack 4023 and reflects light generated in the second LEDstack 4033. The second color filter 4047 transmits light generated inthe first and second LED stacks 4023 and 4033 and reflects lightgenerated in the third LED stack 4043. Accordingly, light generated inthe first LED stack 4023 may be emitted to the outside through thesecond LED stack 4033 and the third LED stack 4043, and light generatedin the second LED stack 4033 may be emitted to the outside through thethird LED stack 4043. Further, it is possible to prevent light generatedin the second LED stack 4033 from being incident on the first LED stack4023 and lost, or light generated in the third LED stack 4043 from beingincident on the second LED stack 4033 and lost.

According to some exemplary embodiments, the first color filter 4037 mayalso reflect light generated in the third LED stack 4043. According tosome exemplary embodiments, when the LED stacks include micro LEDs, thecolor filters may be omitted due to the small form factor of the microLEDs.

The first and second color filters 4037 and 4047 may be, for example, alow pass filter that passes only a low frequency region, that is, a longwavelength region, a band pass filter that passes only a predeterminedwavelength band, or a band stop filter that blocks only thepredetermined wavelength band. In particular, the first and second colorfilters 4037 and 4047 may be formed by alternately stacking insulatinglayers having different refractive indices, and may be formed byalternately stacking, for example, TiO₂ and SiO₂, Ta₂O₅ and SiO₂, Nb₂O₅and SiO₂, HfO₂ and SiO₂, or ZrO₂ and SiO₂. Further, the first and/orsecond color filter 4037 and/or 4047 may include a distributed Braggreflector (DBR). The distributed Bragg reflector may be formed byalternately stacking insulating layers having different refractiveindices. Further, a stop band of the distributed Bragg reflector may becontrolled by adjusting a thickness of TiO₂ and SiO₂.

The first bonding layer 4053 couples the first LED stack 4023 to thesupport substrate 4051. As illustrated, the interconnection line 4029may be in contact with the first bonding layer 4053. In addition, theinterconnection line 4029 is disposed below some regions of the secondinsulating layer 4028, and a region of the second insulating layer 4028that does not have the interconnection line 4029 may be in contact withthe first bonding layer 4053. The first bonding layer 4053 may be lighttransmissive or light non-transmissive. In particular, a contrast of thedisplay apparatus may be improved by using an adhesive layer thatabsorbs light, such as black epoxy, as the first bonding layer 4053.

The first bonding layer 4053 may be in direct contact with the supportsubstrate 4051, but as illustrated, the hydrophilic material layer 4052may be disposed on an interface between the support substrate 4051 andthe first bonding layer 4053. The hydrophilic material layer 4052 maychange a surface of the support substrate 4051 to be hydrophilic toimprove adhesion of the first bonding layer 4053. As used herein, thebonding layer and the hydrophilic material layer may collectively bereferred to as a buffer layer.

The first bonding layer 4053 has a strong adhesion to the hydrophilicmaterial layer, while it has a weak adhesion to a hydrophobic materiallayer. Therefore, peeling may occur at a portion in which the adhesionis weak. The hydrophilic material layer 4052 according to an exemplaryembodiment may change a hydrophobic surface to be hydrophilic to enhancethe adhesion of the first bonding layer 4053, thereby preventing theoccurrence of the peeling.

The hydrophilic material layer 4052 may also be formed by depositing,for example, SiO₂, or others on the surface of the support substrate4051, and may also be formed by treating the surface of the supportsubstrate 4051 with plasma to modify the surface. The surface modifiedlayer increases surface energy to change hydrophobic property intohydrophilic property. In a case in which the second insulating layer4028 has hydrophobic property, the hydrophilic material layer may alsobe disposed on the second insulating layer 4028, and the first bondinglayer 4052 may be in contact with the hydrophilic material layer on thesecond insulating layer 4028.

The second bonding layer 4055 couples the second LED stack 4033 to thefirst LED stack 4023. The second bonding layer 4055 may be disposedbetween the first LED stack 4023 and the first color filter 4037 and maybe in contact with the first color filter 4037. The second bonding layer4055 may transmit light generated in the first LED stack 4023. Ahydrophilic material layer 4054 may be disposed in an interface betweenthe first LED stack 4023 and the second bonding layer 4055. The firstconductivity type semiconductor layer 4023 a of the first LED stack 4023generally exhibits hydrophobic property. Therefore, in a case in whichthe second bonding layer 4055 is in direct contact with the firstconductivity type semiconductor layer 4023 a, the peeling is likely tooccur at an interface between the second bonding layer 4055 and thefirst conductivity type semiconductor layer 4023 a.

The hydrophilic material layer 4054 according to an exemplary embodimentchanges the surface of the first LED stack 4023 from having hydrophobicproperties to having hydrophilic properties, and thus, improves theadhesion of the second bonding layer 4055, thereby reducing orpreventing the occurrence of the peeling. The hydrophilic material layer4054 may be formed by depositing SiO₂ or modifying the surface of thefirst LED stack 4023 with plasma as described above.

A surface layer of the first color filter 4037 which is in contact withthe second bonding layer 4055 may be a hydrophilic material layer, forexample, SiO₂. In a case in which the surface layer of the first colorfilter 4037 is not hydrophilic, the hydrophilic material layer may beformed on the first color filter 4037, and the second bonding layer 4055may be in contact with the hydrophilic material layer.

The third bonding layer 4057 couples the third LED stack 4043 to thesecond LED stack 4033. The third bonding layer 4057 may be disposedbetween the second LED stack 4033 and the second color filter 4047 andmay be in contact with the second color filter 4047. The third bondinglayer 4057 transmits light generated in the first LED stack 4023 and thesecond Led stack 4033. A hydrophilic material layer 4056 may be disposedin an interface between the second LED stack 4033 and the third bondinglayer 4057. The second LED stack 4033 may exhibit hydrophobic property,and as a result, in a case in which the third bonding layer 4057 is indirect contact with the second LED stack 4033, the peeling is likely tooccur at an interface between the third bonding layer 4057 and thesecond LED stack 4033.

The hydrophilic material layer 4056 according to an exemplary embodimentchanges the surface of the second LED stack 4033 from hydrophobicproperty into hydrophilic property, and thus, improves the adhesion ofthe third bonding layer 4057, thereby preventing the occurrence of thepeeling. The hydrophilic material layer 4056 may be formed by depositingSiO₂ or modifying the surface of the second LED stack 4033 with plasmaas described above.

A surface layer of the second color filter 4047 which is in contact withthe third bonding layer 4057 may be a hydrophilic material layer, forexample, SiO₂. In a case in which the surface layer of the second colorfilter 4047 is not hydrophilic, the hydrophilic material layer may beformed on the second color filter 4047 and the third bonding layer 4057may be in contact with the hydrophilic material layer.

The first to third bonding layers 4053, 4055, and 4057 may be formed oflight transmissive SOC, but is not limited thereto, and othertransparent organic material layers or transparent inorganic materiallayers may be used. Examples of the organic material layer may includeSU8, poly(methylmethacrylate) (PMMA), polyimide, parylene,benzocyclobutene (BCB), or others, and examples of the inorganicmaterial layer may include Al₂O₃, SiO₂, SiN_(x), or others. The organicmaterial layers may be bonded at high vacuum and high pressure, and theinorganic material layers may be bonded by planarizing a surface with,for example, a chemical mechanical polishing process, changing surfaceenergy using plasma or others, and then using the changed surfaceenergy.

FIGS. 66A to 66F are schematic cross-sectional views illustrating amethod of manufacturing the light emitting diode stack 4000 for adisplay according to the exemplary embodiment.

Referring to FIG. 66A, a first LED stack 4023 is first grown on a firstsubstrate 4021. The first substrate 4021 may be, for example, a GaAssubstrate. The first LED stack 4023 formed of an AlGaInP basedsemiconductor layers, and includes a first conductivity typesemiconductor layer 4023 a, an active layer, and a second conductivitytype semiconductor layer 4023 b.

Next, the second conductivity type semiconductor layer 4023 b ispartially removed to expose the first conductivity type semiconductorlayer 4023 a. Although FIG. 66A shows only one pixel region, the firstconductivity type semiconductor layer 4023 a is partially exposed foreach of the pixel regions.

A first insulating layer 4027 is formed on the first LED stack 4023 andis patterned to form openings. For example, SiO₂ is formed on the firstLED stack 4023, a photoresist is applied thereto, and a photoresistpattern is formed through photolithograph and development. Next, thefirst insulating layer 4027 in which the openings are formed may beformed by patterning SiO₂ using the photoresist pattern as an etchingmask. One of the openings of the first insulating layer 4027 may bedisposed on the first conductivity type semiconductor layer 4023 a, andother openings may be disposed on the second conductivity typesemiconductor layer 4023 b.

Thereafter, an ohmic contact layer 4025 a and an ohmic electrode 4026are formed in the openings of the first insulating layer 4027. The ohmiccontact layer 4025 a and the ohmic electrode 4026 may be formed using alift-off technique. The ohmic contact layer 4025 a may be first formedand the ohmic electrode 4026 may be then formed, or vice versa. Inaddition, according to an exemplary embodiment, the ohmic electrode 4026and the ohmic contact layer 4025 a may be simultaneously formed of thesame material layer.

After the ohmic contact layer 4025 a is formed, a reflective layer 4025b covering the ohmic contact layer 4025 a and the first insulating layer4027 is formed. The reflective layer 4025 b may be formed using alift-off technique. The reflective layer 4025 b may also cover a portionof the ohmic contact layer 4025 a, and may also cover substantially theentirety of the ohmic contact layer 4025 a as illustrated. A reflectiveelectrode 4025 is formed by the ohmic contact layer 4025 a and thereflective layer 4025 b.

The reflective electrode 4025 may be in ohmic contact with a p-typesemiconductor layer of the first LED stack 4023, and may be thusreferred to as a first p-type reflective electrode 4025. The reflectiveelectrode 4025 is spaced apart from the ohmic electrode 4026, and isthus electrically insulated from the first conductivity typesemiconductor layer 4023 a.

A second insulating layer 4028 covering the reflective electrode 4025and having an opening exposing the ohmic electrode 4026 is formed. Thesecond insulating layer 4028 may be formed of, for example, SiO₂ or SOG.

Then, a interconnection line 4029 is formed on the second insulatinglayer 4028. The interconnection line 4029 is connected to the ohmicelectrode 4026 through the opening of the second insulating layer 4028,and is thus electrically connected to the first conductivity typesemiconductor layer 4023 a.

Although the interconnection line 4029 is illustrated in FIG. 66A ascovering the entire surface of the second insulating layer 4028, theinterconnection line 4029 may be partially disposed on the secondinsulating layer 4028, and an upper surface of the second insulatinglayer 4028 may be exposed around the interconnection line 4029.

Although the illustrated exemplary embodiment shows one pixel region,the first LED stack 4023 disposed on the substrate 4021 may cover aplurality of pixel regions, and the interconnection line 4029 may becommonly connected to the ohmic electrodes 4026 formed on a plurality ofregions. In addition, a plurality of interconnection lines 4029 may beformed on the substrate 4021.

Referring to FIG. 66B, a second LED stack 4033 is grown on a secondsubstrate 4031 and a second-p transparent electrode 4035 and a firstcolor filter 4037 are formed on the second LED stack 4033. The secondLED stack 4033 may include a gallium nitride-based first conductivitytype semiconductor layer 4033 a, a second conductivity typesemiconductor layer 4033 b, and an active layer disposed therebetween,and the active layer may include a GaInN well layer. The secondsubstrate 4031 is a substrate on which a gallium nitride-basedsemiconductor layer may be grown, and is different from the firstsubstrate 4021. A combination ratio of GaInN may be determined so thatthe second LED stack 4033 may emit green light. The second-p transparentelectrode 4035 is in ohmic contact with the second conductivity typesemiconductor layer 4033 b.

The first color filter 4037 may be formed on the second-p transparentelectrode 4035, and since details thereof are substantially the same asthose described with reference to FIG. 65, detailed descriptions thereofwill be omitted in order to avoid redundancy.

Referring to FIG. 66C, a third LED stack 4043 is grown on a thirdsubstrate 4041 and a third-p transparent electrode 4045 and a secondcolor filter 4047 are formed on the third LED stack 4043. The third LEDstack 4043 may include a gallium nitride-based first conductivity typesemiconductor layer 4043 a, a second conductivity type semiconductorlayer 4043 b, and an active layer disposed therebetween, and the activelayer may include a GaInN well layer. The third substrate 4041 is asubstrate on which a gallium nitride-based semiconductor layer may begrown, and is different from the first substrate 4021. A combinationratio of GaInN may be determined so that the third LED stack 4043 emitsblue light. The third-p transparent electrode 4045 is in ohmic contactwith the second conductivity type semiconductor layer 4043 b.

Since the second color filter 4047 is substantially the same as thatdescribed with reference to FIG. 65, detailed descriptions thereof willbe omitted in order to avoid redundancy.

Meanwhile, since the first LED stack 4023, the second LED stack 4033,and the third LED stack 4043 are grown on different substrates, theorder of formation thereof is not particularly limited.

Referring to FIG. 66D, next, the first LED stack 4023 is coupled onto asupport substrate 4051 through the first bonding layer 4053. Bondingmaterial layers may be disposed on the support substrate 4051 and thesecond insulating layer 4028 and may be bonded to each other to form thefirst bonding layer 4053. The interconnection line 4029 is disposed toface the support substrate 4051.

Meanwhile, in a case in which a surface of the support substrate 4051has hydrophobic property, a hydrophilic material layer 4052 may be firstformed on the support substrate 4051. The hydrophilic material layer4052 may also be formed by depositing a material layer such as SiO₂ onthe surface of the support substrate 4051, or treating the surface ofthe support substrate 4051 with plasma or the like to increase surfaceenergy. The surface of the support substrate 4051 is modified by theplasma treatment, and a surface modified layer having high surfaceenergy may be formed on the surface of the support substrate 4051. Thefirst bonding layer 4053 may be bonded to the hydrophilic material layer4052, and adhesion of the first bonding layer 4053 is thus improved.

The first substrate 4021 is removed from the first LED stack 4023 usinga chemical etching technique. Accordingly, the first conductivity typesemiconductor layer of the first LED stack 4023 is exposed on the topsurface. The exposed surface of the first conductivity typesemiconductor layer 4023 a may be textured to increase light extractionefficiency, and a light extraction structure, such as a roughenedsurface or others, may be thus formed on the surface of the firstconductivity type semiconductor layer 4023 a.

Referring to FIG. 66E, the second LED stack 4033 is coupled to the firstLED stack 4023 through the second bonding layer 4055. The first colorfilter 4037 is disposed to face the first LED stack 4023 and is bondedto the second bonding layer 4055. The bonding material layers aredisposed on the first LED stack 4023 and the first color filter 4037 andare bonded to each other to form the second bonding layer 4055.

Meanwhile, before the second bonding layer 4055 is formed, a hydrophilicmaterial layer 4054 may be first formed on the first LED stack 4023. Thehydrophilic material layer 4054 changes the surface of the first LEDstack 4023 from hydrophobic property to hydrophilic property and thusimproves the adhesion of the second bonding layer 4055. The hydrophilicmaterial layer 4054 may also be formed by depositing a material layersuch as SiO₂, or treating the surface of the first LED stack 4023 withplasma or others to increase surface energy. The surface of the firstLED stack 4023 is modified by the plasma treatment, and a surfacemodified layer having high surface energy may be formed on the surfaceof the first LED stack 4023. The second bonding layer 4055 may be bondedto the hydrophilic material layer 4054, and adhesion of the secondbonding layer 4055 is thus improved.

The second substrate 4031 may be separated from the second LED stack4033 using a technique such as a laser lift-off or a chemical lift-off.In addition, in order to improve light extraction, a roughened surfacemay be formed on the exposed surface of the first conductivity typesemiconductor layer 4033 a using a surface texturing.

Referring to FIG. 66F, a hydrophilic material layer 4056 may be thenformed on the second LED stack 4033. The hydrophilic material layer 4056changes the surface of the second LED stack 4033 to hydrophilic propertyand thus improves adhesion of the third bonding layer 4057. Thehydrophilic material layer 4056 may also be formed by depositing amaterial layer such as SiO₂, or treating the surface of the second LEDstack 4033 with plasma or the like to increase surface energy. However,in a case in which the surface of the second LED stack 4033 hashydrophilic property, the hydrophilic material layer 4056 may beomitted.

Next, referring to FIGS. 65 and 66C, the third LED stack 4043 is coupledonto the second LED stack 4033 through the third bonding layer 4057. Thesecond color filter 4047 is disposed to face the second LED stack 4033and is bonded to the third bonding layer 4057. The bonding materiallayers are disposed on the second LED stack 4033 (or the hydrophilicmaterial layer 4056) and the third color filter 4047, and are bonded toeach other to form the third bonding layer 4057.

The third substrate 4041 may be separated from the third LED stack 4043using a technique such as a laser lift-off or a chemical lift-off.Accordingly, as illustrated in FIG. 65, the LED stack for a display inwhich the first conductive layer 4043 a of the third LED stack 4043 isexposed is provided. In addition, a roughened surface may be formed onthe exposed surface of the first conductivity type semiconductor layer4043 a by a surface texturing.

A stack of the first to third LED stacks 4023, 4033, and 4043 disposedon the support substrate 4051 is patterned in a unit of pixel, and thepatterned stacks are connected to each other using the interconnectionlines, thereby making it possible to provide a display apparatus.Hereinafter, a display apparatus according to exemplary embodiments willbe described.

FIG. 67 is a schematic circuit diagram of a display apparatus accordingto an exemplary embodiment, and FIG. 68 is a schematic plan view of adisplay apparatus according to an exemplary embodiment.

Referring to FIGS. 67 and 68, the display apparatus according to anexemplary embodiment may be implemented to be driven in a passive matrixmanner.

For example, since the LED stack for a display described with referenceto FIG. 65 has a structure in which the first to third LED stacks 4023,4033, and 4044 are stacked in a vertical direction, one pixel includesthree light emitting diodes R, G, and B. Here, a first light emittingdiode R may correspond to the first LED stack 4023, a second lightemitting diode G may correspond to the second LED stack 4033, and athird light emitting diode B may correspond to the third LED stack 4043.

In FIGS. 67 and 68, one pixel includes the first to third light emittingdiodes R, G, and B, and each light emitting diode corresponds to asub-pixel. Anodes of the first to third light emitting diodes R, G, andB are connected to a common line, for example, a data line, and cathodesthereof are connected to different lines, for example, scan lines. For afirst pixel, as an example, the anodes of the first to third lightemitting diodes R, G, and B are commonly connected to a data lineVdata1, and cathodes thereof are connected to scan lines Vscan1-1,Vscan1-2, and Vscan1-3, respectively. Accordingly, the light emittingdiodes R, G, and B in the same pixel may be separately driven.

In addition, each of the light emitting diodes R, G, and B may be drivenby using pulse width modulation or change current intensity, therebymaking it possible to adjust brightness of each sub-pixel.

Referring to again FIG. 68, a plurality of patterns are formed bypatterning the stack described with reference to FIG. 65, and therespective pixels are connected to reflective electrodes 4025 andinterconnection lines 4071, 4073, and 4075. As illustrated in FIG. 67,the reflective electrode 4025 may be used as a data line Vdata, and theinterconnection lines 4071, 4073, and 4075 may be formed as the scanlines. Here, the interconnection line 4075 may be formed by theinterconnection line 4029. The reflective electrode 4025 mayelectrically connect the first conductivity type semiconductor layers4023 a, 4033 a, and 4043 a of the first to third LED stacks 4023, 4033,and 4043 of the plurality of pixels to one another, and theinterconnection line 4029 may be disposed to be substantiallyperpendicular to the reflective electrode 4025 to electrically connectthe first conductivity type semiconductor layers 4023 a of the pluralityof pixels to each other.

The pixels may be arranged in a matrix form, and the anodes of the lightemitting diodes R, G, and B of each pixel are commonly connected to thereflective electrode 4025 and the cathodes thereof are each connected tothe interconnection lines 4071, 4073, and 4075 which are spaced apartfrom each other. Here, the interconnection lines 4071, 4073, and 4075may be used as scan lines Vscan.

FIG. 69 is an enlarged plan view of one pixel of the display apparatusof FIG. 68, FIG. 70 is a schematic cross-sectional view taken along lineA-A of FIG. 69, and FIG. 71 is a schematic cross-sectional view takenalong line B-B of FIG. 69.

Referring back to FIGS. 68 to 71, in each pixel, a portion of thereflective electrode 4025, a portion of the second-p transparentelectrode 4035, a portion of an upper surface of the second LED stack4033, a portion of the third-p transparent electrode 4045, and an uppersurface of the third LED stack 4043 are exposed to the outside.

The third LED stack 4043 may have a roughened surface 4043 r formed onthe upper surface thereof. The roughened surface 4043 r may also beformed on the entirety of the upper surface of the third LED stack 4043,or on a portion of the upper surface of the third LED stack 4043.

A lower insulating layer 4061 may cover a side surface of each pixel.The lower insulating layer 4061 may be formed of a light transmissivematerial such as SiO₂, and in this case, the lower insulating layer 4061may also cover substantially the entirety of the upper surface of thethird LED stack 4043. Alternatively, the lower insulating layer 4061according to an exemplary embodiment may include a light reflectivelayer or a light absorption layer to prevent light traveling from thefirst to third LED stacks 4023, 4033, and 4043 to the side surface, andin this case, the lower insulating layer 4061 at least partially exposesthe upper surface of the third LED stack 4043. The lower insulatinglayer 4061 may include, for example, a distribution Bragg reflector or ametallic reflective layer, or an organic reflective layer on atransparent insulating layer, and may also include a light absorptionlayer such as black epoxy. The light absorption layer, such as blackepoxy, may prevent light from being emitted to the outside of thepixels, thereby improving a contrast ratio between the pixels in thedisplay apparatus.

The lower insulating layer 4061 may have an opening 4061 a exposing theupper surface of the third LED stack 4043, an opening 4061 b exposingthe upper surface of the second LED stack 4033, an opening 4061 cexposing the third-p transparent electrode 4045, an opening 4061 dexposing the second-p transparent electrode 4035, and an opening 4061 eexposing the first p-type reflective electrode 4025. The upper surfaceof the first LED stack 4023 may not be exposed to the outside.

The interconnection line 4071 and the interconnection line 4073 may beformed on the support substrate 4051 in the vicinity of the first tothird LED stacks 4023, 4033, and 4043, and may be disposed on the lowerinsulating layer 4061 to be insulated from the first p-type reflectiveelectrode 4025. A connector 4077 ab connects the second-p transparentelectrode 4035 and the third-p transparent electrode 4045 to thereflective electrode 4025. Accordingly, the anodes of the first LEDstack 4023, the second LED stack 4033, and the third LED stack 4043 arecommonly connected to the reflective electrode 4025.

The interconnection line 4075 or 4029 may be disposed to besubstantially perpendicular to the reflective electrode 4025 below thereflective electrode 4025, and is connected to the ohmic electrode 4026,thereby being electrically connected to the first conductivity typesemiconductor layer 4023 a. The ohmic electrode 4026 is connected to thefirst conductivity type semiconductor layer 4023 a below the first LEDstack 4023. The ohmic electrode 4026 may be disposed outside a lowerregion of the roughened surface 4043 r of the third LED stack 4043 asillustrated in FIG. 69, and light loss may be thus reduced.

The connector 4071 a connects the upper surface of the third LED stack4043 to the interconnection line 4071, and the connector 4073 a connectsthe upper surface of the second LED stack 4033 to the interconnectionline 4073.

An upper insulating layer 4081 may be disposed on the interconnectionlines 4071 and 4073 and the lower insulating layer 4061 to protect theinterconnection lines 4071, 4073, and 4075. The upper insulating layer4081 may have openings that expose the interconnection lines 4071, 4073,and 4075, and a bonding wire and the like may be connected theretothrough the openings.

According to an exemplary embodiment, the anodes of the first to thirdLED stacks 4023, 4033, and 4043 are commonly and electrically connectedto the reflective electrode 4025, and the cathodes thereof areelectrically connected to the interconnection lines 4071, 4073, and4075, respectively. Accordingly, the first to third LED stacks 4023,4033, and 4043 may be independently driven. However, the inventiveconcepts are not limited thereto, and connections of the electrodes andwirings can be variously modified.

FIGS. 72A to 72H are schematic plan views for describing a method formanufacturing a display apparatus according to an exemplary embodiment.Hereinafter, a method for manufacturing the pixel of FIG. 69 will bedescribed.

First, the light emitting diode stack 4000 as described with referenceto FIG. 65 is prepared.

Next, referring to FIG. 72A, the roughened surface 4043 r may be formedon the upper surface of the third LED stack 4043. The roughened surface4043 r may be formed to correspond to each pixel region on the uppersurface of the third LED stack 4043. The roughened surface 4043 r may beformed using a chemical etching technique, for example, using aphoto-enhanced chemical etch (PEC) technique.

The roughened surface 4043 r may be partially formed within each pixelregion in consideration of a region in which the third LED stack 4043 isto be etched in the future. In particular, the roughened surface 4043 rmay be formed so that the ohmic electrode 4026 is disposed outside theroughened surface 4043 r. However, the inventive concepts are limitedthereto, and the roughened surface 4043 r may also be formed oversubstantially the entirety of the upper surface of the third LED stack4043.

Referring to FIG. 72B, a peripheral region of the third LED stack 4043is then etched in each pixel region to expose the third-p transparentelectrode 4045. The third LED stack 4043 may be left to havesubstantially a rectangular or square shape as illustrated, but at leasttwo depression parts may be formed along the edges. In addition, asillustrated, one depression part may be formed to be greater thananother depression part.

Referring to FIG. 72C, the exposed third-p transparent electrode 4045 isthen removed except for a portion of the third-p transparent electrode4045 exposed in a relatively large depression part, to thereby exposethe upper surface of the second LED stack 4033. The upper surface of thesecond LED stack 4033 is exposed around the third LED stack 4043 and isalso exposed in another depression part. A region in which the third-ptransparent electrode 4045 is exposed and a region in which the secondLED stack 4033 is exposed are formed in the relatively large depressionpart.

Referring to FIG. 72D, the second LED stack 4033 exposed in theremaining region is removed except for the second LED stack 4033 formedin a relatively small depression part to thereby expose the second-ptransparent electrode 4035. The second-p transparent electrode isexposed around the third LED stack 4043 and the second-p transparentelectrode 4035 is also exposed in the relatively large depression part.

Referring to FIG. 72E, the second-p transparent electrode 4035 exposedaround the second LED stack 4043 is then removed except for the second-ptransparent electrode 4035 exposed in the relatively large depressionpart, to thereby expose the upper surface of the first LED stack 4023.

Referring to FIG. 72F, the first LED stack 4023 exposed around the thirdLED stack 4043 continues to be removed and the first insulating layer4027 is removed to thereby expose the reflective electrode 4025.Accordingly, the reflective electrode 4025 is exposed around the thirdLED stack 4043. The exposed reflective electrode 4025 is patterned so asto have substantially an elongated shape in a vertical direction tothereby form a linear interconnection line. The patterned reflectiveelectrode 4025 is disposed over the plurality of pixel regions in thevertical direction and is spaced apart from a neighboring pixel in ahorizontal direction.

In the illustrated exemplary embodiment, it is described the reflectiveelectrode 4025 is patterned after removing the first LED stack 4023, butthe reflective electrode 4025 may also be formed in advance to have thepatterned shape when the reflective electrode 4025 is formed on thesubstrate 4021. In this case, it is not necessary to pattern thereflective electrode 4025 after removing the first LED stack 4023.

By patterning the reflective electrode 4025, the second insulating layer4028 may be exposed. The interconnection line 4029 is disposed to beperpendicular to the reflective electrode 4025, and is insulated fromthe reflective electrode 4025 by the second insulating layer 4028.

Referring to FIG. 72G, the lower insulating layer 4061 (FIGS. 70 and 71)covering the pixels is then formed. The lower insulating layer 4061covers the reflective electrode 4025 and covers the side surfaces of thefirst to third LED stacks 4023, 4033, and 4043. In addition, the lowerinsulating layer 4061 may at least partially cover the upper surface ofthe third LED stack 4043. In a case in which the lower insulating layer4061 is a transparent layer such as SiO₂, the lower insulating layer4061 may also cover substantially the entirety of the upper surface ofthe third LED stack 4043. Alternatively, the lower insulating layer 4061may also include a reflective layer or a light absorption layer, and inthis case, the lower insulating layer 4061 at least partially exposesthe upper surface of the third LED stack 4043 so that light is emittedto the outside.

The lower insulating layer 4061 may have an opening 4061 a exposing thethird LED stack 4043, an opening 4061 b exposing the second LED stack4033, an opening 4061 c exposing the third-p transparent electrode 4045,an opening 4061 d exposing the second-p transparent electrode 4035, andan opening 4061 e exposing the reflective electrode 4025. One or aplurality of openings 4061 e exposing the reflective electrode 4025 maybe formed.

Referring to FIG. 72H, the interconnection lines 4071 and 4073 and theconnectors 4071 a, 4073 a, and 77 ab are then formed by a lift-offtechnique. The interconnection lines 4071 and 4073 are insulated fromthe reflective electrode 4025 by the lower insulating layer 4061. Theconnector 4071 a electrically connects the third LED stack 4043 to theinterconnection line 4071 and the connector 4073 a connects the secondLED stack 4033 to the interconnection line 4073. The connector 77 abelectrically connects the third-p transparent electrode 4045 and thesecond-p transparent electrode 4035 to the first p-type reflectiveelectrode 4025.

The interconnection lines 4071 and 4073 may be disposed to besubstantially perpendicular to the reflective electrode 4025 and mayconnect the plurality of pixels to each other.

Next, the upper insulating layer 4081 (FIGS. 70 and 71) covers theinterconnection lines 4071 and 4073 and the connectors 4071 a, 4073 a,and 4077 ab. The upper insulating layer 4081 may also coversubstantially the entirety of the upper surface of the third LED stack4043. The upper insulating layer 4081 may be formed of, for example,silicon oxide film or silicon nitride film, and may also include adistribution Bragg reflector. In addition, the upper insulating layer4081 may include a transparent insulating film and a reflective metallayer, or an organic reflective layer of a multilayer structure thereonto reflect light, or may include a light absorption layer such as blackbased epoxy to thereby shield light.

In a case in which the upper insulating layer 4081 reflects or shieldslight, in order to emit light to the outside, it is necessary to atleast partially expose the upper surface of the third LED stack 4043.Meanwhile, in order to allow an electrical connection from the outside,the upper insulating layer 4081 is partially removed to therebypartially expose the interconnection lines 4071, 4073, and 4075.Further, the upper insulating layer 4081 may also be omitted.

As the upper insulating layer 4081 is formed, the pixel regionillustrated in FIG. 69 is completed. In addition, as illustrated in FIG.68, the plurality of pixels may be formed on the support substrate 4051,and those pixels may be connected to each other by the first p-typereflective electrode 4025 and the interconnection lines 4071, 4073, and4075, and may be driven in a passive matrix manner.

In the illustrated exemplary embodiment, the method for manufacturingthe display apparatus that may be driven in the passive matrix manner isdescribed, but the inventive concepts are not limited thereto, and adisplay apparatus including the light emitting diode stack illustratedin FIG. 65 may be configured to be driven in various manners.

For example, it is described that the interconnection lines 4071 and4073 are formed together on the lower insulating layer 4061, but theinterconnection line 4071 may be formed on the lower insulating layer4061 and the interconnection line 4073 may also be formed on the upperinsulating layer 4081.

Meanwhile, in FIG. 65, it is described that the reflective electrode4025, the second-p transparent electrode 4035, and the third-ptransparent electrode 4045 are in ohmic contact with the secondconductivity type semiconductor layers 4023 b, 4033 b, and 4043 b of thefirst LED stack 4023, the second LED stack 4033, and the third LED stack4043, respectively, and it is described that the ohmic electrode 4026 isin ohmic contact with the first conductivity type semiconductor layer4023 a of the first LED stack 4023, but the ohmic contact layer is notseparately provided to the first conductivity type semiconductor layers4033 a and 4033 b of the second LED stack 4033 and the third LED stack4043. When a size of a pixel is as small as 200 micrometers or less,according to some exemplary embodiments, there is no difficulty incurrent dispersion even in a case in which a separate ohmic contactlayer is not formed in the first conductivity type semiconductor layers4033 a and 4043 a, which are n-type. However, for current dispersion,transparent electrode layers may be disposed on the n-type semiconductorlayers of the second and third LED stacks 4033 and 4043.

According to exemplary embodiments, the plurality of pixels may beformed at a wafer level by using the light emitting diode stack 4000 fora display, and thus the steps of individually mounting the lightemitting diodes may be obviated. Furthermore, since the light emittingdiode stack has a structure that the first to third LED stacks 4023,4033, and 4043 are vertically stacked, an area of the sub-pixel may besecured within a limited pixel area. In addition, since light generatedin the first LED stack 4023, the second LED stack 4033, and the thirdLED stack 4043 is transmitted through these LED stacks and emitted tothe outside, it is possible to reduce light loss.

However, the inventive concepts are not limited thereto, and lightemitting to devices in which the respective pixels are separated fromeach other may also be provided, and those light emitting devices areindividually mounted on a circuit board, thereby making it possible toprovide the display apparatus.

In addition, it is described that the ohmic electrode 4026 is formed onthe first conductivity type semiconductor layer 4023 a adjacent to thesecond conductivity type semiconductor layer 4023 b, but the ohmicelectrode 4026 may also be formed on the surface of the firstconductivity type semiconductor layer 4023 a opposite to the secondconductivity type semiconductor layer 4023 b. In this case, the thirdLED stack 4043 and the second LED stack 4033 are patterned to expose theohmic electrode 4026, and instead of the interconnection line 4029, aseparate interconnection line connecting the ohmic electrode 4026 to thecircuit board is provided.

FIG. 73 is a cross-sectional view of a light emitting stacked structureaccording to an exemplary embodiment.

Referring to FIG. 73, a light emitting stacked structure according to anexemplary embodiment includes a plurality of sequentially stackedepitaxial stacks. A plurality of epitaxial stacks are provided on thesubstrate 5010.

The substrate 5010 has a substantially a plate shape having an uppersurface and a lower surface.

A plurality of epitaxial stacks can be mounted on the upper surface ofthe substrate 5010, and the substrate 5010 may be provided in variousforms. The substrate 5010 may be formed of an insulating material.Examples of the material of the substrate 5010 include glass, quartz,silicon, organic polymer, organic/inorganic composite, or others.However, the material of the substrate 5010 is not limited thereto, andis not particularly limited as long as it has an insulation property. Inan exemplary embodiment, the substrate 5010 may further include a wiringpart that may provide a light emitting signal and a common voltage tothe respective epitaxial stacks. In an exemplary embodiment, in additionto the wiring part, the substrate 5010 may further include a driveelement including a thin film transistor, in which case the respectiveepitaxial stacks may be driven in the active matrix type. To this end,the substrate 5010 may be provided as a printed circuit board 5010 or asa composite substrate having a wiring part and/or a drive element formedon glass, silicon, quartz, organic polymer, or organic/inorganiccomposite.

A plurality of epitaxial stacks are sequentially stacked on an uppersurface of the substrate 5010, and respectively emit light.

In an exemplary embodiment, two or more epitaxial stacks may beprovided, each emitting light of different wavelength bands from eachother. That is, a plurality of epitaxial stacks may be provided,respectively having different energy bands from each other. In anexemplary embodiment, the epitaxial stack on the substrate 5010 isillustrated as being provided with three sequentially stacked layers,including first to third epitaxial stacks 5020, 5030, and 5040.

Each of the epitaxial stacks may emit a color light of a visible lightband of various wavelength bands. Light emitted from the lowermostepitaxial stack is a color light of the longest wavelength having thelowest energy band, and the wavelength of the emitted color lightbecomes shorter in the order from lower to upper sides. The lightemitted from the epitaxial stack disposed at the top is a color light ofthe shortest wavelength having the highest energy band. For example, thefirst epitaxial stack 5020 may emit the first color light L1, the secondepitaxial stack 5030 may emit the second color light L2, and the thirdepitaxial stack 5040 may emit the third color light L3. The first tothird color light L1, L2, and L3 correspond to different color lightfrom each other, and the first to third color light L1, L2, and L3 maybe color light of different wavelength bands from each other which havesequentially decreasing wavelengths. That is, the first to third colorlight L1, L2, and L3 may have different wavelength bands from eachother, and the color light may be a shorter wavelength band of a higherenergy in an order of the first color light L1 to the third color lightL3. However, the inventive concepts are not limited thereto, and whenthe light emitting stacked structure include micro LEDs, the lowermostepitaxial stack may emit a color of light having any energy band, andthe epitaxial stacks disposed thereon may emit a color of light havingdifferent energy band than that of the lowermost epitaxial stack due tothe small form factor of micro LEDs.

In the exemplary embodiment, the first color light L1 may be red light,the second color light L2 may be green light, and the third color lightL3 may be blue light, for example.

Each of the epitaxial stacks emits light to a front direction of thesubstrate 5010. In particular, light emitted from one epitaxial stack ispassed through another epitaxial stack located in the light path, andtravels to the front direction. The front direction may corresponds to adirection along which the first to third epitaxial stacks 5020, 5030 and5040 are stacked.

Hereinafter, in addition to the front direction and the back directionmentioned above, the “front” direction of the substrate 5010 will bereferred to as the “upper” direction, and “back” direction of thesubstrate 5010 will be referred to as the “lower” direction. Of course,the terms “upper” or “lower” refer to relative directions, which mayvary according to the placement and the direction of the light emittingstacked structure.

Each of the epitaxial stacks emits light in an upper direction, and eachof the epitaxial stacks transmits most of light emitted from theunderlying epitaxial stacks. In particular, light emitted from the firstepitaxial stack 5020 passes through the second epitaxial stack 5030 andthe third epitaxial stack 5040 and travels to the front direction, andthe light emitted from the second epitaxial stack 5030 passes throughthe third epitaxial stack 5040 and travels to the front direction. Tothis end, at least some, or desirably, all of the epitaxial stacks otherthan the lowermost epitaxial stack may include an optically transmissivematerial. As used herein, the material being “optically transmissive”not only includes a transparent material that transmits the entirelight, but also a material that transmits light of a predeterminedwavelength or transmitting a portion of light of a predeterminedwavelength. In an exemplary embodiment, each of the epitaxial stacks maytransmit about 60% or more of light emitted from the epitaxial stackdisposed thereunder, or about 80% or more in another exemplaryembodiment, or about 90% or more in yet another exemplary embodiment.

In the light emitting stacked structure according to an exemplaryembodiment, the signal lines for applying emitting signals to therespective epitaxial stacks are independently connected, andaccordingly, the respective epitaxial stacks can be independently drivenand the light emitting stacked structure can implement various colorsaccording to whether light is emitted from each of the epitaxial stacks.In addition, the epitaxial stacks for emitting light of differentwavelengths from each other are overlapped vertically on one another,and thus can be formed in a narrow area.

FIGS. 74A and 74B are cross-sectional views illustrating a lightemitting stacked structure according to an exemplary embodiment.

Referring to FIG. 74A, in a light emitting stacked structure accordingto an exemplary embodiment, each of first to third epitaxial stacks5020, 5030, and 5040 may be provided on a substrate 5010 via an adhesivelayer or a buffer layer interposed therebetween.

The adhesive layer 5061 adheres the substrate 5010 and the firstepitaxial stack 5020 onto the substrate 5010. The adhesive layer 5061may include a conductive or non-conductive material. The adhesive layer5061 may have conductivity in some areas, when it needs to beelectrically connected to the substrate 5010 provided thereunder. Theadhesive layer 5061 may include a transparent or opaque material. In anexemplary embodiment, when the substrate 5010 is provided with an opaquematerial and has a wiring part or the like formed thereon, the adhesivelayer 5061 may include an opaque material, for example, a lightabsorbing material. For the light absorbing material that forms theadhesive layer 5061, various polymer adhesives may be used, including,for example, an epoxy-based polymer adhesive.

The buffer layer acts as a component to adhere two adjacent layers toeach other, while also serving to relieve the stress or impact betweentwo adjacent layers. The buffer layer is provided between two adjacentepitaxial stacks to adhere the two adjacent epitaxial stacks together,while also serving to relieve the stress or impact that may affect thetwo adjacent epitaxial stacks.

The buffer layer includes first and second buffer layers 5063 and 5065.The first buffer layer 5063 may be provided between the first and secondepitaxial stacks 5020 and 5030, and a second buffer layer 5065 may beprovided between the second and third epitaxial stacks 5030 and 5040.

The buffer layer includes a material capable of relieving stress orimpact, e.g., a material that is capable of absorbing stress or impactwhen there is stress or impact from the outside. The buffer layer mayhave a certain elasticity for this purpose. The buffer layer may alsoinclude a material having an adhesive force. In addition, the first andsecond buffer layers 5063 and 5065 may include a non-conductive materialand an optically transmissive material. For example, an optically clearadhesive may be used for the first and second buffer layers 5063 and5065.

The material for forming the first and second buffer layers 5063 and5065 is not particularly limited as long as it is optically transparentand is capable of buffering stress or impact while attaching each of theepitaxial stacks stably. For example, the first and second buffer layers5063 and 5065 may be formed of an organic material including anepoxy-based polymer such as SU-8, various resists, parylene, poly(methylmethacrylate) (PMMA), benzocyclobutene (BCB), spin on glass (SOG), orothers, and inorganic material such as silicon oxide, aluminum oxide, orthe like. If necessary, a conductive oxide may also be used as a bufferlayer, in which case the conductive oxide should be insulated from othercomponents. When an organic material is used as the buffer layer, theorganic material may be applied to the adhesive surface and then bondedat a high temperature and a high pressure in a vacuum state. When aninorganic material is used as the buffer layer, the inorganic materialmay be deposited on the adhesive surface and then planarized bychemical-mechanical planarization (CMP) or the like, after which thesurface is subjected to the plasma treatment and then bonded by bondingunder a high vacuum.

Referring to FIG. 74B, each of the first and second buffer layers 5063and 5065 may include an adhesion enhancing layer 5063 a or 5065 a foradhering two epitaxial stacks adjacent to each other, and an shockabsorbing layer 5063 b or 5065 b for relieving stress or impact betweenthe two adjacent epitaxial stacks.

The shock absorbing layer 5063 b and 5065 b between two adjacentepitaxial stacks plays a role of absorbing stress or impact when atleast one of the two adjacent epitaxial stacks is exposed to stress orimpact.

The material that forms the shock absorbing layer 5063 b and 5065 b mayinclude, but is not limited to, silicon oxide, silicon nitride, aluminumoxide, or others. In an exemplary embodiment, the shock absorbing layer5063 b and 5065 b may include silicon oxide.

In an exemplary embodiment, in addition to stress or impact absorption,the shock absorbing layer 5063 b and 5065 b may have a predeterminedadhesion force to adhere two adjacent epitaxial stacks. In particular,the shock absorbing layer 5063 b and 5065 b may include a material withsurface energy similar or equivalent to the surface energy of theepitaxial stack to facilitate adhesion to the epitaxial stack. Forexample, when the surface of the epitaxial stack is imparted withhydrophilicity through a plasma treatment or others, a hydrophilicmaterial such as silicon oxide may be used as the shock absorbing layerin order to improve adhesion to the hydrophilic epitaxial stack.

The adhesion enhancing layer 5063 a or 5065 a serves to firmly adheretwo adjacent epitaxial stacks. Examples of the material for forming theadhesion enhancing layer 5063 a or 5065 a include, but are not limitedto, epoxy-based polymers such as SOG, SU-8, various resists, parylene,poly(methyl methacrylate) (PMMA), benzocyclobutene (BCB), or others. Inan exemplary embodiment, the adhesion enhancing layer 5063 a or 5065 amay include SOG.

In an exemplary embodiment, the first buffer layer 5063 may include afirst adhesion enhancing layer 5063 a and a first shock absorbing layer5063 b, and the second buffer layer 5065 may include a second adhesionenhancing layer 5065 a and a second shock absorbing layer 5065 b. In anexemplary embodiment, each of the adhesion enhancing layer and the shockabsorbing layer may be provided as one layer, but are not limitedthereto, and in another exemplary embodiment, each of the adhesionenhancing layer and the shock absorbing layer may be provided as aplurality of layers.

In an exemplary embodiment, the order of stacking the adhesion enhancinglayer and the shock absorbing layer may be variously changed. Forexample, the shock absorbing layer may be stacked on the adhesionenhancing layer, or conversely, the adhesion enhancing layer may bestacked on the shock absorbing layer. In addition, the order of stackingthe adhesion enhancing layer and the shock absorbing layer in the firstbuffer layer 5063 and the second buffer layer 5065 may be different. Forexample, in the first buffer layer 5063, the first shock absorbing 5063b layer and the first adhesion enhancing layer 5063 a may besequentially stacked, while in the second buffer layer 5065, the firstadhesion enhancing layer 5065 a and the second shock absorbing layer5065 b may be stacked sequentially. FIG. 74B shows an exemplaryembodiment where the first shock absorbing layer 5063 b is stacked onthe first adhesion enhancing layer 5063 a in the first buffer layer5063, and the second shock absorbing layer 5065 b is stacked on thesecond adhesion enhancing layer 5065 a in the second buffer layer 5065.

In an exemplary embodiment, the thicknesses of the first buffer layer5063 and the second buffer layer 5065 may be substantially the same aseach other or different from each other. The thicknesses of the firstbuffer layer 5063 and the second buffer layer 5065 may be determined inconsideration of the amount of impact to the epitaxial stacks in thestacking process of the epitaxial stacks. In an exemplary embodiment,the thickness of the first buffer layer 5063 may be greater than thethickness of the second buffer layer 5065. In particular, the thicknessof the first shock absorbing layer 5063 b in the first buffer layer 5063may be greater than the thickness of the second shock absorbing layer5065 b in the second buffer layer 5065.

The light emitting stacked structure according to an exemplaryembodiment may be manufactured through a process in which the first tothird epitaxial stacks 5020, 5030, and 5040 are stacked sequentially,and accordingly, the second epitaxial stack 5030 is stacked after thefirst epitaxial stack 5020 is stacked, and the third epitaxial stack5040 is stacked after both the first and second epitaxial stacks 5020and 5030 are stacked. Accordingly, the amount of stress or impact thatmay be applied to the first epitaxial stack 5020 during a process isgreater than the amount of stress or impact that may be applied to thesecond epitaxial stack 5030, and with an increased frequency. Inparticular, since the second epitaxial stack 5030 is stacked in a statethat the stack thereunder has a shallow thickness, the second epitaxialstack 5030 is subjected to a greater amount of stress or impact than thestress or impact exerted to the third epitaxial stack 5040 that isstacked on the underlying stack of a relatively greater thickness. In anexemplary embodiment, the thickness of the first buffer layer 5063 isgreater than the thickness of the second buffer layer 5065 to compensatefor the difference in stress or impact mentioned above.

FIG. 75 is a cross-sectional view of a light emitting stacked structureaccording to an exemplary embodiment.

Referring to FIG. 75, each of the first to third epitaxial stacks 5020,5030, and 5040 may be provided on the substrate 5010 via the adhesivelayer 5061 and the first and second buffer layers 5063 and 5065interposed therebetween.

Each of the first to third epitaxial stacks 5020, 5030, and 5040includes p-type semiconductor layers 5025, 5035, and 5045, active layers5023, 5033, and 5043, and n-type semiconductor layers 5021, 5031, and5041, which are sequentially disposed.

The p-type semiconductor layer 5025, the active layer 5023, and then-type semiconductor layer 5021 of the first epitaxial stack 5020 mayinclude a semiconductor material that emits red light.

Examples of a semiconductor material that emits red light may includealuminum gallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP),aluminum gallium indium phosphide (AlGaInP), gallium phosphide (GaP), orothers. However, the semiconductor material that emits red light is notlimited thereto, and various other materials may be used.

A first p-type contact electrode 5025 p may be provided under the p-typesemiconductor layer 5025 of the first epitaxial stack 5020. The firstp-type contact electrode 5025 p of the first epitaxial stack 5020 may bea single layer or a multi-layer metal. For example, the first p-typecontact electrode 5025 p may include various materials including metalssuch as Al, Ti, Cr, Ni, Au, Ag, Ti, Sn, Ni, Cr, W, Cu, or others, oralloys thereof. The first p-type contact electrode 5025 p may includemetal having a high reflectivity, and accordingly, since the firstp-type contact electrode 5025 p is formed of metal having a highreflectivity, it is possible to increase the emission efficiency oflight emitted from the first epitaxial stack 5020 in the upperdirection.

A first n-type contact electrode 5021 n may be provided on an upperportion of the n-type semiconductor layer of the first epitaxial stack5020. The first n-type contact electrode 5021 n of the first epitaxialstack 5020 may be a single layer or a multi-layer metal. For example,the first n-type contact electrode 5021 n may be formed of variousmaterials including metals such as Al, Ti, Cr, Ni, Au, Ag, Ti, Sn, Ni,Cr, W, Cu, or others, or alloys thereof. However, the material of thefirst n-type contact electrode 5021 n is not limited to those mentionedabove, and accordingly, other conductive materials may be used.

The second epitaxial stack 5030 includes an n-type semiconductor layer5031, an active layer 5033, and a p-type semiconductor layer 5035, whichare sequentially disposed. The n-type semiconductor layer 5031, theactive layer 5033, and the p-type semiconductor layer 5035 may include asemiconductor material that emits green light. Examples of materials foremitting to green light include indium gallium nitride (InGaN), galliumnitride (GaN), gallium phosphide (GaP), aluminum gallium indiumphosphide (AlGaInP), and aluminum gallium phosphide (AlGaP). However,the semiconductor material that emits green light is not limitedthereto, and various other materials may be used.

A second p-type contact electrode 5035 p is provided under the p-typesemiconductor layer 5035 of the second epitaxial stack 5030. The secondp-type contact electrode 5035 p is provided between the first epitaxialstack 5020 and the second epitaxial stack 5030, or specifically, betweenthe first buffer layer 5063 and the second epitaxial stack 5030.

Each of the second p-type contact electrodes 5035 p may include atransparent conductive oxide (TCO). The transparent conductive oxide mayinclude tin oxide (SnO), indium oxide (InO2), zinc oxide (ZnO), indiumtin oxide (ITO), indium tin zinc oxide (ITZO) or others. The transparentconductive compound may be deposited by the chemical vapor deposition(CVD), the physical vapor deposition (PVD), such as an evaporator, asputter, or others. The second p-type contact electrode 5035 p may beprovided with a sufficient thickness to serve as an etch stopper in thefabrication process to be described below, for example, with a thicknessof about 5001 angstroms to about 2 micrometers to the extent that thetransparency is satisfied.

The third epitaxial stack 5040 includes a p-type semiconductor layer5045, an active layer 5043, and an n-type semiconductor layer 5041,which are sequentially disposed. The p-type semiconductor layer 5045,the active layer 5043, and the n-type semiconductor layer 5041 mayinclude a semiconductor material that emits blue light. The examples ofthe materials that emit blue light may include gallium nitride (GaN),indium gallium nitride (InGaN), zinc selenide (ZnSe), or others.However, the semiconductor material that emits blue light is not limitedthereto, and various other materials may be used.

A third p-type contact electrode 5045 p is provided under the p-typesemiconductor layer 5045 of the third epitaxial stack 5040. The thirdp-type contact electrode 5045 p is provided between the second epitaxialstack 5030 and the third epitaxial stack 5040, or specifically, betweenthe second buffer layer 5065 and the third epitaxial stack 5040.

The second p-type contact electrode 5035 p and the third p-type contactelectrode 5045 p between the p-type semiconductor layer 5035 of thesecond epitaxial stack 5030, and the p-type semiconductor layer 5045 ofthe third epitaxial stack 5040 are shared electrodes shared by thesecond epitaxial stack 5030 and the third epitaxial stack 5040.

Since the second p-type contact electrode 5035 p and the third p-typecontact electrode 5045 p are at least partially in contact with eachother, and physically and electrically connected to each other, when asignal is applied to at least a portion of the second p-type contactelectrode 5035 p or the third p-type contact electrode 5045 p, the samesignal can be applied to the p-type semiconductor layer 5035 of thesecond epitaxial stack 5030 and the p-type semiconductor layer 5045 ofthe third epitaxial stack 5040 at the same time. For example, when acommon voltage is applied to one of the second p-type contact electrode5035 p and the third p-type contact electrode 5045 p, the common voltageis applied to the p-type semiconductor layers of each of the second andthird epitaxial stacks 5030 and 5040 through both the second p-typecontact electrode 5035 p and the third p-type contact electrode 5045 p.

In the illustrated exemplary embodiment, although the n-typesemiconductor layers 5021, 5031, and 5041 and the p-type semiconductorlayers 5025, 5035, and 5045 of the first to third epitaxial stacks 5020,5030, and 5040 are each shown as a single layer, these layers may bemultilayers and may also include superlattice layers. In addition, theactive layers 5023, 5033, and 5043 of the first to third epitaxialstacks 5020, 5030, and 5040 may include a single quantum well structureor a multi-quantum well structure.

In an exemplary embodiment, the second and third p-type contactelectrodes 5035 p and 5045 p, which are shared electrodes, substantiallycover the second and third epitaxial stacks 5030 and 5040. The secondand third p-type contact electrodes 5035 p and 5045 p may include atransparent conductive material to transmit light from the epitaxialstack below. For example, each of the second and third p-type contactelectrodes 5035 p and 5045 p may include a transparent conductive oxide(TCO). The transparent conductive oxide may include tin oxide (SnO),indium oxide (InO2), zinc oxide (ZnO), indium tin oxide (ITO), indiumtin zinc oxide (ITZO) or others. The transparent conductive compound maybe deposited by the chemical vapor deposition (CVD), the physical vapordeposition (PVD), such as an evaporator, a sputter, or others. Thesecond and third p-type contact electrodes 5035 p and 5045 p may beprovided with a sufficient thickness to serve as an etch stopper in thefabrication process to be described below, for example, with a thicknessof about 5001 angstroms to about 2 micrometers to the extent that thetransparency is satisfied.

In an exemplary embodiment, common lines may be connected to the firstto third p-type contact electrodes 5025 p, 5035 p, and 5045 p. In thiscase, the common line is a line to which the common voltage is applied.In addition, the light emitting signal lines may be connected to then-type semiconductor layers 5021, 5031, and 5041 of the first to thirdepitaxial stacks 5020, 5030, and 5040, respectively. A common voltage SCis applied to the first p-type contact electrode 5025 p, the secondp-type contact electrode 5035 p, and the third p-type contact electrode5045 p through the common line, and the light emitting signal is appliedto the n-type semiconductor layer 5021 of the first epitaxial stack5020, the n-type semiconductor layer 5031 of the second epitaxial stack5030, and the n-type semiconductor layer 5041 of the third epitaxialstack 5040 through the light emitting signal line, thereby controllingthe light emission of the first to third epitaxial stacks 5020, 5030,and 5040. The light emitting signal includes first to third lightemitting signals SR, S_(G), and SB corresponding to the first to thirdepitaxial stacks 5020, 5030, and 5040, respectively. In an exemplaryembodiment, the first light emitting signal SR may be a signalcorresponding to red light, the second light emitting signal S_(G) maybe a signal corresponding to green light, and the third light emittingsignal SB may be a signal corresponding to an emission of blue light.

In the illustrated exemplary embodiment described above, it is describedthat a common voltage is applied to the p-type semiconductor layers5025, 5035, and 5045 of the first to third epitaxial stacks 5020, 5030,and 5040, and the light emitting signal is applied to the n-typesemiconductor layers 5021, 5031, and 5041 of the first to thirdepitaxial stacks 5020, 5030, and 5040, but the inventive concepts arenot limited thereto. In another exemplary embodiment, a common voltagemay be applied to the n-type semiconductor layers 5021, 5031, and 5041of the first to third epitaxial stacks 5020, 5030, and 5040, and lightemitting signals may be applied to the p-type semiconductor layers 5025,5035, and 5045 of the first to third epitaxial stacks 5020, 5030, and5040.

In this manner, the first to third epitaxial stacks 5020, 5030, and 5040are driven according to a light emitting signal applied to each of theepitaxial stacks. In particular, the first epitaxial stack 5020 isdriven according to a first light emitting signal SR, the secondepitaxial stack 5030 is driven according to a second light emittingsignal SG, and the third epitaxial stack 5040 is driven according to thethird light emitting signal SB. In this case, the first, second, andthird driving signals SR, SG, and SB are independently applied to thefirst to third epitaxial stacks 5020, 5030, and 5040, and as a result,each of the first to third epitaxial stacks 5020, 5030 and 5040 isindependently driven. The light emitting stacked structure may finallyprovide light of various colors by combining the first to third colorlight emitted upward from the first to third epitaxial stacks 5020,5030, and 5040.

The light emitting stacked structure according to an exemplaryembodiment may implement a color in a manner such that portions ofdifferent color light are provided on the overlapped region, rather thanimplementing different color light on different planes spaced apart fromeach other, thereby advantageously providing compactness and integrationof the light emitting element. In a conventional light emitting element,in order to realize full color, light emitting elements that emitdifferent colors, such as red, green, and blue light are generallyplaced apart from each other on a plane, which would occupy a relativelylarge area as each of the light emitting elements is arranged on aplane. However, in the light emitting stacked structure according to anexemplary embodiment, it is possible to realize a full color in aremarkably smaller area compared to the conventional light emittingelement, by providing a stacked structure having the portions of thelight emitting elements that emit different color light overlapped inone region. Accordingly, it is possible to manufacture a high-resolutiondevice even in a small area.

In addition, the light emitting stacked structure according to anexemplary embodiment significantly reduces defects that may occur duringmanufacture. In particular, the light emitting stacked structure can bemanufactured by stacking in the order of the first to third epitaxialstacks, in which case the second epitaxial stack is stacked in a statethat the first epitaxial stack is stacked, and the third epitaxial stackis stacked in a state that both the first and second epitaxial stacksare stacked. However, since the first to third epitaxial stacks arefirst manufactured on a separate temporary substrate, and then stackedby being transferred onto the substrate, defects may occur during thestep of transferring onto the substrate and removing the temporarysubstrate, the first to third epitaxial stacks and other components onthe first to third epitaxial stacks may be exposed to stress or impact.However, since the light emitting stacked structure according to anexemplary embodiment includes a buffer layer, or a stress or shockabsorbing layer, between adjacent epitaxial stacks, defects that mayoccur during processing may be reduced.

In addition, the conventional light emitting device has a complexstructure and thus requires a complicated manufacturing process, as itwould require separately preparing respective light emitting elementsand then forming separate contacts such as connecting by interconnectionlines, or others, for each of the light emitting elements. However,according to an exemplary embodiment, the light emitting stackedstructure is formed by stacking multi-layers of epitaxial stackssequentially on a single substrate 5010, and then forming contacts onthe multi-layered epitaxial stacks and connecting by lines through aminimum process. In addition, since light emitting elements ofindividual colors are separately manufactured and mounted separately,only a single light emitting stacked structure is mounted according toan exemplary embodiment, instead of a plurality of light emittingelements. Accordingly, the manufacturing method is simplifiedsignificantly.

The light emitting stacked structure according to an exemplaryembodiment may additionally employ various components to provide highpurity and color light of high efficiency. For example, a light emittingstacked structure according to an exemplary embodiment may include awavelength pass filter to block short wavelength light from proceedingtoward the epitaxial stack that emits relatively long wavelength light.

In the following exemplary embodiments, in order to avoid redundantdescriptions, differences from the exemplary embodiments described abovewill be mainly described.

FIG. 76 is a cross-sectional view of a light emitting stacked structureincluding a predetermined wavelength pass filter according to anexemplary embodiment.

Referring to FIG. 76, a first wavelength pass filter 5071 may beprovided between the first epitaxial stack 5020 and the second epitaxialstack 5030 in a light emitting stacked structure according to anexemplary embodiment.

The first wavelength pass filter 5071 selectively transmits a certainwavelength light, and may transmit a first color light emitted from thefirst epitaxial stack 5020 while blocks or reflects light other than thefirst color light. Accordingly, the first color light emitted from thefirst epitaxial stack 5020 may travel in an upper direction, while thesecond and third color light emitted from the second and third epitaxialstacks 5030 and 5040 are blocked from traveling toward the firstepitaxial stack 5020, and may be reflected or blocked by the firstwavelength pass filter 5071.

The second and third color light are high-energy light that may have arelatively shorter wavelength than the first color light, which mayadditional light emission in the first epitaxial stack 5020 whenentering the first epitaxial stack 5020. In an exemplary embodiment, thesecond and the third color light may be blocked from entering the firstepitaxial stack 5020 by the first wavelength pass filter 5071.

In an exemplary embodiment, a second wavelength pass filter 5073 may beprovided between the second epitaxial stack 5030 and the third epitaxialstack 5040. The second wavelength pass filter 5073 transmits the firstcolor light and the second color light emitted from the first and secondepitaxial stacks 5020 and 5030, while blocking or reflecting light otherthan the first and second color light. Accordingly, the first and secondcolor light emitted from the first and second epitaxial stacks 5020 and5030 may travel in the upper direction, while the third color lightemitted from the third epitaxial stack 5040 is not allowed to travel ina direction toward the first and second epitaxial stacks 5020 and 5030,but reflected or blocked by the second wavelength pass filter 5073.

As described above, the third color light is a relatively high-energylight having a shorter wavelength than the first and second color light,and when entering the first and second epitaxial stacks 5020 and 5030,the third color light may induce additional emission in the first andsecond epitaxial stacks 5020 and 5030. In an exemplary embodiment, thesecond wavelength pass filter 5073 prevents the third light fromentering the first and second epitaxial stacks 5020 and 5030.

The first and second wavelength pass filters 5071 and 5073 may be formedin various shapes, and may be formed by alternately stacking insulatingfilms having different refractive indices. For example, the wavelengthof transmitted light may be determined by alternately stacking SiO₂ andTiO₂, and adjusting the thickness and number of stacking of SiO₂ andTiO₂. The insulating films having different refractive indices mayinclude SiO₂, TiO₂, HfO₂, Nb₂O₅, ZrO₂, Ta₂O₅, or others.

When the first and second wavelength pass filters 5071 and 5073 areformed by stacking inorganic insulating films having differentrefractive indices from each other, defects due to stress or impactduring the manufacturing process, for example, peel-off or cracks mayoccur. However, according to an exemplary embodiment, such defects maybe significantly reduced by providing a buffer layer to relieve theimpact.

The light emitting stacked structure according to an exemplaryembodiment may additionally employ various components to provide uniformlight of high efficiency. For example, a light emitting stackedstructure according to an exemplary embodiment may have variousirregularities (or roughened surface) on the light exit surface. Forexample, a light emitting stacked structure according to an exemplaryembodiment may have irregularities formed on an upper surface of atleast one n-type semiconductor layer of the first to third epitaxialstacks 5020, 5030, and 5040.

In an exemplary embodiment, the irregularities of each of the epitaxialstacks may be selectively formed. For example, irregularities may beprovided on the first epitaxial stack 5020, irregularities may beprovided on the first and third epitaxial stacks 5020 and 5040, orirregularities may be provided on the first to third epitaxial stacks5020, 5030 and 5040. The irregularities of each of the epitaxial stacksmay be provided on an n-type semiconductor layer corresponding to theemission surface of each of the epitaxial stacks.

The irregularities are provided to increase light emission efficiency,and may be provided in various forms such as a polygonal pyramid, ahemisphere, or planes with a surface roughness in a random arrangement.The irregularities may be textured through various etching processes orby using a patterned sapphire substrate.

In an exemplary embodiment, the first to third color light from thefirst to third epitaxial stacks 5020, 5030, and 5040 may have differentlight intensities, and this difference in intensity may lead todifferences in visibility. The light emission efficiency may be improvedby selectively forming irregularities on the light exit surface of thefirst to third epitaxial stacks 5020, 5030 and 5040, which results inreduction of the visibility differences between the first to third colorlight. The color light corresponding to red and/or blue color may havelower visibility than the green color, in which case the first epitaxialstack 5020 and/or the third epitaxial stack 5040 may be textured todecrease the difference of visibility. In particularly, when thelowermost of the light emitting stacks emits red color light, the lightintensity may be small. As such, the light efficiency may be increasedby forming irregularities on the upper surface thereof.

The light emitting stacked structure having the structure describedabove is a light emitting element capable of expressing various colors,and thus may be employed as a pixel in a display device. In thefollowing exemplary embodiment, a display device will be described asincluding the light emitting stacked structure according to exemplaryembodiments.

FIG. 77 is a plan view of a display device according to an exemplaryembodiment, and FIG. 78 is an enlarged plan view illustrating portion P1of FIG. 77.

Referring to FIGS. 77 and 78, the display device 5110 according to anexemplary embodiment may display any visual information such as text,video, photographs, two or three-dimensional images, or others.

The display device 5110 may be provided in various shapes including aclosed polygon that includes a straight side, such as a rectangle, or acircle, an ellipse, or the like, that includes a curved side, asemi-circle, or semi-ellipse that includes a combination of straight andcurved sides. In an exemplary embodiment, the display device will bedescribed as having substantially a rectangular shape.

The display device 5110 has a plurality of pixels 5110 for displayingimages. Each of the pixels 5110 may be a minimum unit for displaying animage. Each pixel 5110 includes the light emitting stacked structurehaving the structure described above, and may emit white light and/orcolor light.

In an exemplary embodiment, each pixel includes a first pixel 5110R thatemits red light, a second pixel 5110G that emits green light, and athird pixel 5110B that emits blue light. The first to third pixels5110R, 5110G, and 5110B may correspond to the first to third epitaxialstacks 5020, 5030, and 5040 of the light emitting stacked structuredescribed above, respectively.

The pixels 5110 are arranged in a matrix. As used herein, pixelsarranged in “a matrix” may not only refer to when the pixels 5110 arearranged in a line along the row or column, but also to when the pixels5110 are arranged in any repeating pattern, such as generally along therows and columns, with certain modifications in details, such as thepixels 5110 being arranged in a zigzag shape, for example.

FIG. 79 is a structural diagram of a display device according to anexemplary embodiment.

Referring to FIG. 79, a display device 5110 according to an exemplaryembodiment includes a timing controller 5350, a scan driver 5310, a datadriver 5330, a wiring part, and pixels. When the pixels include aplurality of pixels, each of the pixels is individually connected to thescan driver 5310, the data driver 5330, or the like through a wiringpart.

The timing controller 5350 receives various control signals and imagedata necessary for driving a display device from outside (e.g., from asystem for transmitting image data). The timing controller 5350rearranges the received image data and transmits the image data to thedata driver 5330. In addition, the timing controller 5350 generates scancontrol signals and data control signals necessary for driving the scandriver 5310 and the data driver 5330, and outputs the generated scancontrol signals and data control signals to the scan driver 5310 and thedata driver 5330.

The scan driver 5310 receives scan control signals from the timingcontroller 5350 and generates corresponding scan signals. The datadriver 5330 receives data control signals and image data from the timingcontroller 5350, and generates corresponding data signals.

The wiring part includes a plurality of signal lines. The wiring partincludes scan lines 5130 connecting the scan driver 5310 and the pixels,and data lines 5120 connecting the data driver 5330 and the pixels. Thescan lines 5130 may be connected to respective pixels, and accordingly,the scan lines 5130 that correspond to the respective pixels are markedas first to third scan lines 5130R, 5130G, and 5130B (hereinafter,collectively referred to by ‘5130’).

In addition, the wiring part further includes lines connecting betweenthe timing controller 5350 and the scan driver 5310, the timingcontroller 5350 and the data driver 5330, or other components, andtransmitting the signals.

The scan lines 5130 provide the scan signals generated at the scandriver 5310 to the pixels. The data signals generated at the data driver5330 is outputted to the data lines 5120.

The pixels are connected to the scan lines 5130 and data lines 5120. Thepixels selectively emit light in response to the data signals inputtedfrom the data lines 5120 when the scan signals are supplied from scanlines 5130. For example, during each frame period, each of the pixelsemits light with the luminance corresponding to the input data signals.The pixels supplied with data signals corresponding to black luminancedisplay black by emitting no light during the corresponding frameperiod.

In an exemplary embodiment, the pixels may be driven as either passiveor active type. When the display device is driven as the active type,the display device may be supplied with the first and second pixelpowers in addition to the scan signals and the data signals.

FIG. 80 is a circuit diagram of one pixel of a passive type displaydevice. The pixel may be one of R, G, B pixels, and the first pixel5110R is illustrated as an example. Since the second and third pixelsmay be driven in substantially the same manner as the first pixel, thecircuit diagrams for the second and third pixels will be omitted.

Referring to FIG. 80, a first pixel 5110R includes a light emittingelement 150 connected between a scan line 5130 and a data line 5120. Thelight emitting element 150 may correspond to the first epitaxial stack5020. The first epitaxial stack 5020 emits light with a luminancecorresponding to a magnitude of the applied voltage when a voltage equalto or greater than a threshold voltage is applied between the p-typesemiconductor layer and the n-type semiconductor layer. In particular,the emission of the first pixel 5110R may be controlled by controllingthe voltages of the scan signal applied to the first scan line 5130Rand/or the data signal applied to the data line 5120.

FIG. 81 is a circuit diagram of a first pixel of an active type displaydevice.

When the display device is the active type, the first pixel 5110R may befurther supplied with the first and second pixel powers (ELVDD andELVSS) in addition to the scan signal and the data signal.

Referring to FIG. 81, the first pixel 5110R includes a light emittingelement 150 and a transistor part connected thereto. The light emittingelement 150 may correspond to the first epitaxial stack 5020, and thep-type semiconductor layer of the light emitting element 150 may beconnected to the first pixel power ELVDD via the transistor part, andthe n-type semiconductor layer may be connected to a second pixel powerELVSS. The first pixel power ELVDD and the second pixel power ELVSS mayhave different potentials from each other. For example, the second pixelpower ELVSS may have potential lower than that of the first pixel powerELVDD, by at least the threshold voltage of the light emitting element.Each of these light emitting elements emits light with a luminancecorresponding to the driving current controlled by the transistor part.

According to an exemplary embodiment, the transistor part includes firstand a second transistors M1 and M2 and a storage capacitor Cst. However,the inventive concepts are not limited thereto, and the structure of thetransistor part may be varied.

The source electrode of the first transistor M1 (e.g., switchingtransistor) is connected to the data line 5120, and the drain electrodeis connected to the first node N1. Further, the gate electrode of thefirst transistor is connected to the first scan line 5130R. The firsttransistor is turned on when a scan signal of a voltage capable ofturning on the first transistor M1 is supplied from the first scan line5130R to the data line 5120, to electrically connect the first node Ni.The data signal of the corresponding frame is supplied to the data line5120, and accordingly, the data signal is transmitted to the first nodeNi. The data signal transmitted to the first node Ni is charged in thestorage capacitor Cst.

The source electrode of the second transistor M2 is connected to thefirst pixel power ELVDD, and the drain electrode is connected to then-type semiconductor layer of the light emitting element. The gateelectrode of the second transistor M2 is connected to the first node Ni.The second transistor M2 controls an amount of driving current suppliedto the light emitting element corresponding to the voltage of the firstnode N1.

One electrode of the storage capacitor Cst is connected to the firstpixel power ELVDD, and the other electrode is connected to the firstnode Ni. The storage capacitor Cst charges the voltage corresponding tothe data signal supplied to the first node Ni and maintains the chargedvoltage until the data signal of the next frame is supplied.

FIG. 81 shows a transistor part including two transistors. However, theinventive concepts are not limited thereto, and various modificationsare applicable to the structure of the transistor part. For example, thetransistor part may include more transistors, capacitors, or the like.In addition, although the specific structures of the first and secondtransistors, storage capacitors, and lines are not shown, the first andsecond transistors, storage capacitors, and lines are not particularlylimited and can be variously provided.

The pixels may be implemented in various structures within the scope ofthe inventive concepts. Hereinafter, a pixel according to an exemplaryembodiment will be described with reference to a passive matrix typepixel.

FIG. 82 is a plan view of a pixel according to an exemplary embodiment,and FIGS. 83A and 83B are cross-sectional views taken along lines I-I′and II-II′ of FIG. 82, respectively.

Referring to FIGS. 82, 83A and 83B, viewing from a plan view, a pixelaccording to an exemplary embodiment includes a light emitting region inwhich a plurality of epitaxial stacks are stacked, and a peripheralregion surrounding the light emitting region. The plurality of epitaxialstacks include first to third epitaxial stacks 5020, 5030, and 5040.

When viewed from a plan view, the pixel according to an exemplaryembodiment has a light emitting region in which a plurality of epitaxialstacks are stacked. At least one side of the light emitting region isprovided with a contact for connecting the wiring part to the first tothird epitaxial stacks 5020, 5030, and 5040. The contact includes firstand second common contacts 5050GC and 5050BC for applying a commonvoltage to the first to third epitaxial stacks 5020, 5030, and 5040, afirst contact 5020C for providing a light emitting signal to the firstepitaxial stack 5020, a second contact 5030C for providing a lightemitting signal to the second epitaxial stack 5030, and a third contact5040C for providing a light emitting signal to the third epitaxial stack5040.

In an exemplary embodiment, the stacked structure may vary depending onthe polarity of the semiconductor layers of the first to third epitaxialstacks 5020, 5030, and 5040 to which the common voltage is applied. Thatis, regarding the first and second common contacts 5050GC and 5050BC,when there are contact electrodes provided for applying a common voltageto each of the first to third epitaxial stacks 5020, 5030, and 5040,such contact electrodes may be referred to as the “first to third commoncontact electrodes”, and the first to third contact electrodes may bethe “first to third p-type contact electrodes”, respectively, when thecommon voltage is applied to the p-type semiconductor layer. In anexemplary embodiment where a common voltage is applied to the n-typesemiconductor layer, the first to third common contact electrodes may befirst to third n-type contact electrodes, respectively. Hereinafter, acommon voltage will be described as being applied to a p-typesemiconductor layer, and thus, the first to third common contactelectrodes will be described as corresponding to first to third p-typecontact electrodes, respectively.

In an exemplary embodiment, when viewed from a plan view, the first andsecond common contacts 5050GC and 5050BC and the first to third contacts5020C, 5030C, and 5040C may be provided at various positions. Forexample, when the light emitting stacked structure has substantially asquare shape, the first and second common contacts 5050GC and 5050BC andthe first to third contacts 5020C, 5030C, and 5040C may be disposed inregions corresponding to respective corners of the square. However, thepositions of the first and second common contacts 550GC and 550BC andthe first to third contacts 5020C, 5030C and 5040C are not limitedthereto, and various modifications are applicable according to the shapeof the light emitting stacked structure.

The plurality of epitaxial stacks include first to third epitaxialstacks 5020, 5030, and 5040. The first to third epitaxial stacks 5020,5030, and 5040 are connected with first to third light emitting signallines for providing light emitting signals to each of the first to thirdepitaxial stacks 5020, 5030, and 5040, and a common line for providing acommon voltage to each of the first to third epitaxial stacks 5020,5030, and 5040. In an exemplary embodiment, the first to third lightemitting signal lines may correspond to the first to third scan lines5130R, 5130G, and 5130B, and the common line may correspond to the dataline 5120. Accordingly, the first to third scan lines 5130R, 5130G, and5130B and the data line 5120 are connected to the first to thirdepitaxial stacks 5020, 5030, and 5040, respectively.

In an exemplary embodiment, the first to third scan lines 5130R, 5130G,and 5130B may extend substantially in a first direction (e.g., in atransverse direction as shown in the drawing). The data line 5120 mayextend substantially in a second direction intersecting with the firstto third scan lines 5130R, 5130G, and 5130B (e.g., in a longitudinaldirection as shown in the drawing). However, the extending directions ofthe first to third scan lines 5130R, 5130G, and 5130B and the data line5120 are not limited thereto, and various modifications are applicableaccording to the arrangement of the pixels.

The data line 5120 and the first p-type contact electrode 5025 p extendsubstantially in a second direction intersecting the first direction,while concurrently providing a common voltage to the p-typesemiconductor layer of the first epitaxial stack 5020. Accordingly, thedata line 5120 and the first p-type contact electrode 5025 p may besubstantially the same component. Hereinafter, the first p-type contactelectrode 5025 p may be referred to as the data line 5120 or vice versa.

An ohmic electrode 5025 p′ for ohmic contact between the first p-typecontact electrode 5025 p and the first epitaxial stack 5020 is providedon the light emitting region provided with the first p-type contactelectrode 5025 p.

The first scan line 5130R is connected to the first epitaxial stack 5020through the first contact hole CH1, and the data line 5120 is connectedvia the ohmic electrode 5025 p′. The second scan line 5130G is connectedto the second epitaxial stack 5030 through the second contact hole CH2and the data line 5120 is connected through the 4 a ^(th) and 4 b ^(th)contact holes CH4 a and CH4 b. The third scan line 5130B is connected tothe third epitaxial stack 5040 through the third contact hole CH3 andthe data line 5120 is connected through the 5 a ^(th) and 5 b ^(t)hcontact holes CH5 a and CH5 b.

A buffer layer, a contact electrode, a wavelength pass filter, or thelike are provided between the substrate 5010 and the first to thirdepitaxial stacks 5020, 5030, and 5040, respectively. Hereinafter, thepixel according to an exemplary embodiment will be described in theorder of stacking.

According to an exemplary embodiment, a first epitaxial stack 5020 isprovided on the substrate 5010 via an adhesive layer 5061 interposedtherebetween. In the first epitaxial stack 5020, a p-type semiconductorlayer, an active layer, and an n-type semiconductor layer aresequentially disposed from lower to upper sides.

A first insulating film 5081 is stacked on a lower surface of the firstepitaxial stack 5020, that is, on the surface facing the substrate 5010.A plurality of contact holes are formed in the first insulating film5081. The contact holes are provided with an ohmic electrode 5025 p′ incontact with the p-type semiconductor layer of the first epitaxial stack5020. The ohmic electrode 5025 p′ may include a variety of materials. Inan exemplary embodiment, the ohmic electrode 5025 p′ corresponding tothe p-type ohmic electrode 5025 p′ may include an Au/Zn alloy or anAu/Be alloy. In this case, since the material of the ohmic electrode5025 p′ is to lower in reflectivity than Ag, Al, Au, or the like,additional reflective electrodes may be further disposed. As anadditional reflective electrode, Ag, Au, or the like may be used, andTi, Ni, Cr, Ta, or the like may be disposed as an adhesive layer foradhesion to adjacent components. In this case, the adhesive layer may bethinly deposited on the upper and lower surfaces of the reflectiveelectrode including Ag, Au, or the like.

The first p-type contact electrode 5025 p and the data line 5120 are incontact with the ohmic electrode 5025 p′. The first p-type contactelectrode 5025 p (also serving as the data line 5120) is providedbetween the first insulating film 5081 and the adhesive layer 5061.

When viewed from a plan view, the first p-type contact electrode 5025 pmay be provided in a form such that the first p-type contact electrode5025 p overlaps the first epitaxial stack 5020, or more particularly,overlaps the light emitting region of the first epitaxial stack 5020,while covering most, or all of the light emitting region. The firstp-type contact electrode 5025 p may include a reflective material sothat the first p-type contact electrode 5025 p may reflect light fromthe first epitaxial stack 5020. The first insulating film 81 may also beformed to have a reflective property to facilitate the reflection oflight from the first epitaxial stack 5020. For example, the firstinsulating film 81 may have an omni-directional reflector (ODR)structure.

In addition, the material of the first p-type contact electrode layer5025 p is selected from metals having high reflectivity to light emittedfrom the first epitaxial stack 5020, to maximize the reflectivity oflight emitted from the first epitaxial stack 5020. For example, when thefirst epitaxial stack 5020 emits red light, metal having a highreflectivity to red light, for example, Au, Al, Ag, or the like may beused as the material of the first p-type contact electrode layer 5025 p.Au does not have a high reflectivity to light emitted from the secondand third epitaxial stacks 5030 and 5040 (e.g., green light and bluelight), and thus can reduce a mixture of colors by light emitted fromthe second and third epitaxial stacks 5030 and 5040.

The first wavelength pass filter 5071 and the first n-type contactelectrode 5021 n are provided on an upper surface of the first epitaxialstack 5020. In an exemplary embodiment, the first n-type contactelectrode 5021 n may include various metals and metal alloys, includingAu/Te alloy or Au/Ge alloy, for example.

The first wavelength pass filter 5071 is provided on the upper surfaceof the first epitaxial stack 5020 to cover substantially all the lightemitting region of the first epitaxial stack 5020.

The first n-type contact electrode 5021 n is provided in a regioncorresponding to the first contact 5020C and may include a conductivematerial. The first wavelength pass filter 5071 is provided with acontact hole through which the first n-type contact electrode 5021 n isbrought into contact with the n-type semiconductor layer on the uppersurface of the first epitaxial stack 5020.

The first buffer layer 5063 is provided on the first epitaxial stack5020, and the second p-type contact electrode 5035 p and the secondepitaxial stack 5030 are sequentially provided on the first buffer layer5063. In the second epitaxial stack 5030, a p-type semiconductor layer,an active layer, and an n-type semiconductor layer are sequentiallydisposed from lower to upper sides.

In an exemplary embodiment, the region corresponding to the firstcontact 5020C of the second epitaxial stack 5030 is removed, therebyexposing a portion of the upper surface of the first n-type contactelectrode 5021 n. In addition, the second epitaxial stack 5030 may havea smaller area than the second p-type contact electrode 5035 p. Theregion corresponding to the first common contact 550GC is removed fromthe second epitaxial stack 5030, thereby exposing to a portion of theupper surface of the second p-type contact electrode 5035 p.

The second wavelength pass filter 5073, the second buffer layer 5065,and the third p-type contact electrode 5045 p are sequentially providedon the second epitaxial stack 5030. The third epitaxial stack 5040 isprovided on the third p-type contact electrode 5045 p. In the thirdepitaxial stack 5040, an n-type semiconductor layer, an active layer,and a p-type semiconductor layer are sequentially disposed from lower toupper sides.

The third epitaxial stack 5040 may have a smaller area than the secondepitaxial stack 5030. The third epitaxial stack 5040 may have a smallerarea than the third p-type contact electrode 5045 p. The regioncorresponding to the second common contact 5050BC is removed from thethird epitaxial stack 5040, thereby exposing a portion of the uppersurface of the third p-type contact electrode 5045 p.

The second insulating film 5083 covering the stacked structure of thefirst to third epitaxial stacks 5020, 5030, and 5040 is provided on thethird epitaxial stack 5040. The second insulating film 5083 may includevarious organic/inorganic insulating materials, but is not limitedthereto. For example, the second insulating film 5083 may includeinorganic insulating material including silicon nitride and siliconoxide, or organic insulating material including polyimide.

The first contact hole CH1 is formed in the second insulating film 5083to expose an upper surface of the first n-type contact electrode 5021 nprovided in the first contact 5020C. The first scan line is connected tothe first n-type contact electrode 5021 n through the first contact holeCH1.

A third insulating film 5085 is provided on the second insulating film5083. The third insulating film 5085 may include a materialsubstantially the same as or different from the second insulating film5083. The third insulating film 5085 may include variousorganic/inorganic insulating materials, but is not limited thereto.

The second and third scan lines 5130G and 5130B and the first and secondbridge electrodes BR_(G) and BR_(B) are provided on the third insulatingfilm 5085.

The third insulating film 5085 is provided with a second contact holeCH2 for exposing an upper surface of the second epitaxial stack 5030 atthe second contact 5030C, that is, exposing the n-type semiconductorlayer of the second epitaxial stack 5030, a third contact hole CH3 forexposing an upper surface of the third epitaxial stack 5040 at the thirdcontact 5040C, that is, exposing an n-type semiconductor layer of thethird epitaxial stack 5040, 4 a ^(th) and 4 b ^(th) contact holes CH4 aand CH4 b for exposing an upper surface of the first p-type contactelectrode 5025 p and an upper surface of the second p-type contactelectrode 5035 p, at the first common contact 5050GC, and 5 a ^(th) and5 b ^(t)h contact holes CH5 a and CH5 b for exposing an upper surface ofthe first p-type contact electrode 5025 p and an upper surface of thethird p-type contact electrode 5045 p, at the second common contact5050BC.

The second scan line 5130G is connected to the n-type semiconductorlayer of the second epitaxial stack 5030 through the second contact holeCH2. The third scan line 5130B is connected to the n-type semiconductorlayer of the third epitaxial stack 5040 through the third contact holeCH3.

The data line 5120 is connected to the second p-type contact electrode5035 p through the 4 a ^(th) and 4 b ^(th) contact holes CH4 a and CH4 band the first bridge electrode BR_(G). The data line 5120 is alsoconnected to the third p-type contact electrode 5045 p through the 5 a^(th) and 5 b ^(th) contact holes CH5 a and CH5 b and the second bridgeelectrode BR_(B).

It is illustrated herein that the second and third scan lines 5130G and5130B in an exemplary embodiment are electrically connected to then-type semiconductor layer of the second and third epitaxial stacks 5030and 5040 in direct contact with each other. However, in anotherexemplary embodiment, the second and third n-type contact electrodes maybe further provided between the second and third scan lines 5130G and5130B and the n-type semiconductor layers of the second and thirdepitaxial stacks 5030 and 5040.

According to an exemplary embodiment, irregularities may be selectivelyprovided on the upper surfaces of the first to third epitaxial stacks5020, 5030, and 5040, that is, on an upper surface of the n-typesemiconductor of the first to third epitaxial stacks. Each of theirregularities may be provided only at a portion corresponding to thelight emitting region, or may be provided over the entire upper surfaceof the respective semiconductor layers.

In addition, in an exemplary embodiment, a substantially,non-transmissive film may be further provided on sides of the secondand/or third insulating films 5083 and 5085 that correspond to the sidesof the pixel. The non-transmissive film is a light blocking film thatincludes a light absorbing or reflective material, which is provided toprevent light from the first to third epitaxial stacks 5020, 5030, and5040 from emerging through the sides of the pixel.

In an exemplary embodiment, the optically non-transmissive film may beformed as a single or multi-layered metal. For example, the opticallynon-transmissive film may be formed of a variety of materials includingmetals such as Al, Ti, Cr, Ni, Au, Ag, Ti, Sn, Ni, Cr, W, Cu or others,or alloys thereof.

The optically non-transmissive film may be provided on the side of thesecond insulating film 5083 as a separate layer formed of a materialsuch as metal or alloy thereof.

The optically non-transmissive film may be provided in such a form thatis laterally extending from at least one of the first to third scanlines 5130R, 5130G, and 5130B and the first and second bridge electrodesBR_(G) and BR_(B). In this case, the optically non-transmissive filmextending from one of the first to third scan lines 5130R, 5130G, and5130B and the first and second bridge electrodes BR_(G) and BR_(B) isprovided within a limit such that it is not electrically connected toother conductive components.

In addition, a substantially, non-transmissive film may be provided,which is formed separately from the first to third scan lines 5130R,5130G, and 5130B and the first and second bridge electrodes BR_(G) andBR_(B), on the same layer and using substantially the same materialduring the same process of forming at least one of the first to thirdscan lines 5130R, 5130G, and 5130B and the first and second bridgeelectrodes BR_(G) and BR_(B). In this case, the non-transmissive filmmay be electrically insulated from the first to third scan lines 5130R,5130G, and 5130B and the first and second bridge electrodes BR_(G) andBR_(B).

Alternatively, when no optically non-transmissive film is separatelyprovided, the second and third insulating films 5083 and 5085 may serveas optically non-transmissive films. When the second and thirdinsulating films 5083 and 5085 are used as an optically non-transmissivefilm, the second and third insulating films 5083 and 5085 may not beprovided in a region corresponding to an upper portion (front direction)of the first to third epitaxial stacks 5020, 5030, and 5040 to allowlight emitted from the first to third epitaxial stacks 5020, 5030, and5040 to travel to the front direction.

The substantially, non-transmissive film is not particularly limited aslong as it blocks transmission of light by absorbing or reflectinglight. In an exemplary embodiment, the non-transmissive film may be adistributed Bragg reflector (DBR) dielectric mirror, a metal reflectivefilm formed on an insulating film, or an organic polymer film in blackcolor. When a metal reflective film is used as the non-transmissivefilm, the metal reflective film may be in a floating state that iselectrically isolated from the components within other pixels.

By providing the non-transmissive film on the sides of the pixels, it ispossible to prevent the phenomenon in which light emitted from a certainpixel affects adjacent pixels, or in which color is mixed with lightemitted from the adjacent pixels.

The pixel having the structure described above may be manufactured bysequentially stacking the first to third epitaxial stacks 5020, 5030,and 5040 on the substrate 5010 sequentially and patterning the same,which will be described in detail below.

FIGS. 84A to 84C are cross-sectional views of line I-I′ in FIG. 82,illustrating a process of stacking first to third epitaxial stacks on asubstrate.

Referring to FIG. 84A, the first epitaxial stack 5020 is formed on thesubstrate 5010.

The first epitaxial stack 5020 and the ohmic electrode 5025 p′ areformed on a first temporary substrate 5010 p. In an exemplaryembodiment, the first temporary substrate 5010 p may be a semiconductorsubstrate such as a GaAs substrate for forming the first epitaxial stack5020. The first epitaxial stack 5020 is fabricated in a manner ofstacking the n-type semiconductor layer, the active layer, and thep-type semiconductor layer on the first temporary substrate 5010 p. Thefirst insulating film 5081 having a contact hole formed thereon isformed on the first temporary substrate 5010 p, and the ohmic electrode5025 p′ is formed within the contact hole of the first insulating film5081.

The ohmic electrode 5025 p′ is formed by forming the first insulatingfilm 81 on the first temporary substrate 5010 p, applying photoresist,patterning the photoresist, depositing an ohmic electrode 5025 p′material on the patterned photoresist, and then lifting off thephotoresist pattern. However, the method of forming the ohmic electrode5025 p′ is not limited thereto. For example, the first insulating film81 may be formed by forming the first insulating film 81, patterning thefirst insulating film 81 by photolithography, forming the ohmicelectrode film 5025 p′ with the ohmic electrode film 5025 p′ materialand then patterning the ohmic electrode film 5025 p′ byphotolithography.

The first p-type contact electrode layer 5025 p (also serving as thedata line 5120) formed on the first temporary substrate 5010 p on whichthe ohmic electrode 5025 p′ is formed. The first p-type contactelectrode layer 5025 p may include a reflective material. The firstp-type contact electrode layer 5025 p may be formed by, for example,depositing a metallic material and then patterning the same usingphotolithography.

The first epitaxial stack 5020 formed on the first temporary substrate5010 p is inverted and attached to the substrate 5010 via the adhesivelayer 5061 interposed therebetween.

After the first epitaxial stack 5020 is attached to the substrate 5010,the first temporary substrate 5010 p is removed. The first temporarysubstrate 5010 p may be removed by various methods such as wet etching,dry etching, physical removal, laser lift-off, or the like.

Referring to FIG. 84B, after the first temporary substrate 5010 p isremoved, the first n-type contact electrode 5021 n, the first wavelengthpass filter 5071, and the first adhesion enhancing layer 5063 a areformed on the first epitaxial stack 5020. The first n-type contactelectrode 5021 n may be formed by depositing a conductive material andthen patterning by the photolithography process. The first wavelengthpass filter 5071 may be formed by alternately stacking insulating filmshaving different refractive indices from each other.

After the removal of the first temporary substrate 5010 p,irregularities may be formed on an upper surface (n-type semiconductorlayer) of the first epitaxial stack 5020. The irregularities may beformed by texturing with various etching processes. For example, theirregularities may be formed by various methods such as dry etchingusing a micro photo process, wet etching using a crystal characteristic,texturing using a physical method such as sand blasting, ion beametching, texturing based on difference in etching rates of blockcopolymers, or the like.

The second epitaxial stack 5030, the second p-type contact electrodelayer 5035 p, and the first shock absorbing layer 5063 b are formed on aseparate second temporary substrate 5010 q.

The second temporary substrate 5010 q may be a sapphire substrate. Thesecond epitaxial stack 5030 may be fabricated by forming the n-typesemiconductor layer, the active layer, and the p-type semiconductorlayer on the second temporary substrate 5010 q.

The second epitaxial stack 5030 formed on the second temporary substrate5010 q is inverted and attached onto the first epitaxial stack 5020. Inthis case, the first adhesion enhancing layer 5063 a and the secondshock absorbing layer 5063 b may be disposed to face each other and thenjoined. In an exemplary embodiment, the first adhesion enhancing layer5063 a and the first shock absorbing layer 5063 b may include variousmaterials, such as SOG and silicon oxide, respectively.

After attachment, the second temporary substrate 5010 q is removed. Thesecond temporary substrate 5010 q may be removed by various methods suchas wet etching, dry etching, physical removal, laser lift-off, or thelike.

According to an exemplary embodiment, in the process of attaching thesecond epitaxial stack 5030 formed on the second temporary substrate5010 q onto the substrate 5010, and in the process of removing thesecond temporary substrate 5010 q from the second epitaxial stack 5030,the impact applied to the first epitaxial stack 5020, the secondepitaxial stack 5030, the first wavelength pass filter 5071, and thesecond p-type contact electrode 5035 p, is absorbed and/or relieved bythe first buffer layer 5063, more particularly, by the first shockabsorbing layer 5063 b within the first layer 5063. This minimizescracking and peel-off that may otherwise occur in the first epitaxialstack 5020, the second epitaxial stack 5030, the first wavelength passfilter 5071, and the second p-type contact electrode 5035 p. Moreparticularly, when the first wavelength pass filter 5071 is formed onthe upper surface of the first epitaxial stack 5020, the possibility ofhaving peel-off is remarkably reduced as compared to when the firstwavelength pass filter 5071 is formed on the second epitaxial stack 5030side. When the first wavelength pass filter 5071 is formed on the uppersurface of the second epitaxial stack 5030 and then attached to thefirst epitaxial stack 5020 side, due to impact generated in the processof removing the second temporary substrate 5010 q, there may be apeel-off defect of the first wavelength pass filter 5071. However,according to an exemplary embodiment, in addition to the firstwavelength pass filter 5071 being formed on the first epitaxial stack5020 side, the shock absorbing effect by the first shock absorbing layer5063 b may prevent the occurrence of defects, such as peel-off.

Referring to FIG. 84C, the second wavelength pass filter 5073 and thesecond adhesion enhancing layer 5065 a are formed on the secondepitaxial stack 5030 from which the second temporary substrate 5010 qhas been removed.

The second wavelength pass filter 5073 may be formed by alternatelystacking insulating films having different refractive indices from eachother.

Irregularities may be formed on an upper surface (n-type semiconductorlayer) of the second epitaxial stack 5030 after the removal of thesecond temporary substrate. The irregularities may be textured throughvarious etching processes, or may be formed by using a patternedsapphire substrate for the second temporary substrate.

The third epitaxial stack 5040, the third p-type contact electrode layer5045 p, and the second shock absorbing layer 5065 b are formed on aseparate third temporary substrate 5010 r.

The third temporary substrate 5010 r may be a sapphire substrate. Thethird epitaxial stack 5040 may be fabricated by forming the n-typesemiconductor layer, the active layer, and the p-type semiconductorlayer on the third temporary substrate 5010 r.

The third epitaxial stack 5040 formed on the third temporary substrate5010 r is inverted and attached onto the second epitaxial stack 5030. Inthis case, the second adhesion enhancing layer 5065 a and the secondshock absorbing layer 5065 b may be disposed to face each other and thenjoined. In an exemplary embodiment, the second adhesion enhancing layer5065 a and the second shock absorbing layer 5065 b may include variousmaterials, such as SOG and silicon oxide, respectively.

After attachment, the third temporary substrate 5010 r is removed. Thethird temporary substrate 5010 r may be removed by various methods suchas wet etching, dry etching, physical removal, laser lift-off, or thelike.

According to an exemplary embodiment, in the process of attaching thethird epitaxial stack 5040 formed on the third temporary substrate 5010r onto the substrate 5010, and in the process of removing the thirdtemporary substrate 5010 r from the third epitaxial stack 5040, theimpact applied to the second and third epitaxial stacks 5030 and 5040,the second wavelength pass filter 5073, and the third p-type contactelectrode 5045 p is absorbed and/or relieved by the second buffer layer5065, in particular, by the second shock absorbing layer 5065 b withinthe second buffer layer 5065.

Accordingly, all of the first to third epitaxial stacks 5020, 5030, and5040 are stacked on the substrate 5010.

Irregularities may be formed on an upper surface (n-type semiconductorlayer) of the third epitaxial stack 5040 after the removal of the secondtemporary substrate. The irregularities may be textured through variousetching processes or may be formed by using a patterned sapphiresubstrate for the second temporary substrate 5010 q.

Hereinafter, a method of manufacturing a pixel by patterning stackedepitaxial stacks according to an exemplary embodiment will be described.

FIGS. 85, 87, 89, 91, 93, 95, and 97 are plan views sequentially showinga method of manufacturing a pixel on a substrate according to anexemplary embodiment.

FIGS. 86A, 86B, 88A, 88B, 90A, 90B, 92A, 92B, 94A, 94B, 96A, 96B, 98A,and 98B are views taken along line I-I′ and line II-II′ of correspondingfigures, respectively.

Referring to FIGS. 85, 86A and 86B, first, the third epitaxial stack5040 is patterned. Most of the third epitaxial stack 5040 except for thelight emitting region is removed and in particular, the portionscorresponding to the first and second contacts 5030C and the first andsecond common contacts 5050GC and 5050BC are removed. The thirdepitaxial stack 5040 may be removed by various methods such as wetetching or dry etching using photolithography, and the third p-typecontact electrode 5045 p may function as an etch stopper.

Referring to FIGS. 87, 88A, and 88B, the third p-type contact electrode5045 p, the second buffer layer 5065, and the second wavelength passfilter 5073 are removed from the region excluding the light emittingregion. As such, a portion of the upper surface of the second epitaxialstack 5030 is exposed at the second contact 5030C.

The third p-type contact electrode 5045 p, the second buffer layer 5065,and the second wavelength pass filter 5073 may be removed by variousmethods such as wet etching or to dry etching using photolithography.

Referring to FIGS. 89, 90A, to 90, a portion of the second epitaxialstack 5030 is removed, exposing a portion of the upper surface of thesecond p-type contact electrode 5035 p at the second common contact5050GC to the outside. The third p-type contact electrode 5045 p servesas an etch stopper during etching.

Next, portions of the second p-type contact electrode 5035 p, the firstbuffer layer 5063, and the first wavelength pass filter 5071 are etched.Accordingly, the upper surface of the first n-type contact electrode5021 n is exposed at the first contact 5020C, and the upper surface ofthe first epitaxial stack 5020 is exposed at the portions other than thelight emitting region.

The second epitaxial stack 5030, the second p-type contact electrode5035 p, the first buffer layer 5063, and the first wavelength passfilter 5071 may be removed by various methods such as wet etching or dryetching using photolithography.

Referring to FIGS. 91, 92A, and 92B, the first epitaxial stack 5020 andthe first insulating film 5081 are etched in the region excluding thelight emitting region. The upper surface of the first p-type contactelectrode 5025 p is exposed at the first and second common contacts5050GC and 5050BC.

Referring to FIGS. 93, 94A, and 94B, the second insulating film 5083 isformed on the front side of the substrate 5010, and first to thirdcontact holes CH1, CH2, CH3, the 4 a ^(th) and 4 b ^(th) contact holesCH4 a and CH4 b, and the 5 a ^(th) and 5 b ^(th) contact holes CH5 a andCH5 b are formed.

After deposition, the second insulating film 5083 may be patterned byvarious methods such as wet etching or dry etching usingphotolithography.

Referring to FIGS. 95, 96A, and 96B, the first scan line 5130R is formedon the patterned second insulating film 5083. The first scan line 5130Ris connected to the first n-type contact electrode 5021 n through thefirst contact hole CH1 at the first contact 5020C.

The first scan line 5130R may be formed in various ways. For example,the first scan line 5130R may be formed by photolithography using aplurality of sheets of masks.

Next, the third insulating film 5085 is formed on the front side of thesubstrate 5010, and the second and third contact holes CH2 and CH3, the4 a ^(th) and 4 b ^(th) contact holes CH4 a and CH4 b, and the 5 a ^(th)and 5 b ^(th) contact holes CH5 a and CH5 b are formed.

After deposition, the third insulating film 5085 may be patterned byvarious methods such as wet etching or dry etching usingphotolithography.

Referring to FIGS. 97, 98A, and 98B, the second scan line 5130G, thethird scan line 5130B, the first bridge electrode BR_(G), and the secondbridge electrode BR_(B) are formed on a patterned third insulating film5085.

The second scan line 5130G is connected to the n-type semiconductorlayer of the second epitaxial stack 5030 through the second contact holeCH2 at the second contact 5030C. The third scan line 5130B is connectedto the n-type semiconductor layer of the fourth epitaxial stack 5040through a third contact hole CH3 at the third contact 5040C. The firstbridge electrode BR_(G) is connected to the first p-type contactelectrode 5025 p through the 4 a ^(th) and 4 b ^(th) contact holes CH4 aand CH4 b at the first common contact 5050GC. The second bridgeelectrode BR_(B) is connected to the first p-type contact electrode 5025p through the 5 a ^(th) and 5 b ^(th) contact holes CH5 a and CH5 b atthe second common contact 5050BC.

The second scan line 5130G, the third scan line 5130B and the bridgeelectrode 5120 b may be formed on the third insulating film 5085 invarious ways, for example, by photolithography using a plurality ofsheets of masks.

The second scan line 5130G, the third scan line 5130B and the first andsecond bridge electrodes BR_(G) and BR_(B) may be formed by applyingphotoresist on the substrate 5010 on which the third insulating film5085 is formed, and then patterning the photoresist, and depositingmaterials of the second scan line, the third scan line, and the bridgeelectrode on the patterned photoresist and then lifting off thephotoresist pattern.

According to an exemplary embodiment, the order of forming the first tothird scan lines 5130R, 5130G, and 5130B and the first and second bridgeelectrodes BR_(G) and BR_(B) of the wiring part is not particularlylimited, and may be formed in various sequences. For example, it isillustrated that the second scan line 5130G, the third scan line 5130B,and the first and second bridge electrodes BR_(G) and BR_(B) are formedon the third insulating film 5085 in the same stage, but they may beformed in a different order. For example, the first scan line 5130R andthe second scan line 5130G may be first formed in the same step,followed by the formation of the additional insulating film and then thethird scan line 5130B. Alternatively, the first scan line 5130R and thethird scan line 5130B may be formed first in the same step, followed bythe formation of the additional insulating film, and then the formationof the second scan line 5130G. In addition, the first and second bridgeelectrodes BR_(G) and BR_(B) may be formed together at any of the stepsof forming the first to third scan lines 5130R, 5130G, and 5130B.

In addition, in an exemplary embodiment, the positions of the contactsof the respective epitaxial stacks 5020, 5030, and 5040 may be formeddifferently, in which case the positions of the first to third scanlines 5130R, 5130G, and 5130B and the first and second bridge electrodesBR_(G) and BR_(B) may also be changed.

In an exemplary embodiment, an optically non-transmissive film may befurther provided on the second insulating film 5083 or the thirdinsulating film 5085, on the fourth insulating film corresponding to theside of the pixel. The optically non-transmissive film may be formed ofa DBR dielectric mirror, a metal reflective film on an insulating film,or an organic polymer film. When a metal reflective film is used as theoptically non-transmissive film, it is manufactured in a floating statethat is electrically insulated from the components in other pixels. Inan exemplary embodiment, the optically non-transmissive film may beformed by depositing two or more insulating films with refractiveindices different from each other. For example, the opticallynon-transmissive film may be formed by stacking a material having a lowrefractive index and a material having a high refractive index insequence, or alternatively, formed by alternately stacking insulatingfilms having different refractive indices from each other. Materialshaving different refractive indices are not particularly limited, butexamples thereof include SiO₂ and SiN_(x).

As described above, in a display device according to an exemplaryembodiment, it is possible to sequentially stack a plurality ofepitaxial stacks and then form contacts with a wiring part at aplurality of epitaxial stacks at the same time.

FIG. 99 is a schematic plan view of a display apparatus according to anembodiment, FIG. 100A is a partial cross-sectional view of FIG. 99, andFIG. 100B is a schematic circuit diagram.

Referring to FIGS. 99 and 100A, the display apparatus may include asubstrate 6021, a plurality of pixels, a first LED stack 6100, a secondLED stack 6200, a third LED stack 6300, an insulating layer (or a bufferlayer) 6130 having a multilayer structure, a first color filter 6230, asecond color filter 6330, a first adhesive layer 6141, a second adhesivelayer 6161, a third adhesive layer 6261, and a barrier 6350. Inaddition, the display apparatus may include various electrode pads andconnectors.

The substrate 6021 supports semiconductor stacks 6100, 6200, and 6300.Further, the substrate 6021 may have a circuit therein. For example, thesubstrate 6021 may be a silicon substrate in which thin film transistorsare formed therein. TFT substrates are widely used for active matrixdriving of a display field, such as in an LCD display field, or thelike. Since a configuration of a TFT substrate is well known in the art,detailed descriptions thereof will be omitted. A plurality of pixels maybe driven in an active matrix manner, but the inventive concepts are notlimited thereto. In another exemplary embodiment, the substrate 6021 mayinclude a passive circuit including data lines and scan lines, and thus,the plurality of pixels may be driven in a passive matrix manner.

A plurality of pixels may be arranged on the substrate 6021. The pixelsmay be spaced apart from each other by a barrier 6350. The barrier 6350may be formed of a light reflecting material or a light absorbingmaterial. The barrier 6350 may block light traveling toward aneighboring pixel region by reflection or absorption, thereby preventinglight interference between pixels. Examples of the light reflectingmaterial may include a light reflecting material, such as a white photosensitive solder resistor (PSR), and examples of the light absorbingmaterial may include black epoxy, or others.

Each pixel includes the first to third LED stacks 6100, 6200, and 6300.The second LED stack 6200 is disposed on the first LED stack 6100 andthe third LED stack 6300 is disposed on the second LED stack 6200.

The first LED stack 6100 includes an n-type semiconductor layer 6123 anda p-type semiconductor layer 6125, the second LED stack 6200 includes ann-type semiconductor layer 6223 and a p-type semiconductor layer 6225,and the third LED stack 6300 includes an n-type semiconductor layer 6323and a p-type semiconductor layer 6325. In addition, the first to thirdLED stacks 6100, 6200, and 6300 each include an active layer interposedbetween the n-type semiconductor layer 6123, 6223, or 6323 and thep-type semiconductor layer 6125, 6225 or 6325. The active layer mayhave, in particular, a multiple quantum well structure.

As an LED stack is positioned closer to the substrate 6021, the LEDstack may emit light with a longer wavelength. For example, the firstLED stack 6100 may be an inorganic light emitting diode that emits redlight, the second LED stack 6200 may be an inorganic light emittingdiode that emits green light, and the third LED stack 6300 may be aninorganic light emitting diode that emits blue light. For example, thefirst LED stack 6100 may include an AlGaInP-based well layer, the secondLED stack 6200 may include an AlGaInP-based or AlGaInN-based well layer,and the third LED stack 6300 may include an AlGaInN-based well layer.However, the inventive concepts are not limited thereto. In particular,when LED stacks include micro LEDs, an LED stack disposed closer to thesubstrate 6021 may emit light with a shorter wavelength, and LED stacksdisposed thereon may emit light with a longer wavelength withoutadversely affection operation or requiring color filters due to thesmall form factor of a micro LED.

An upper surface of each of the first to third LED stacks 6100, 6200,and 6300 may be n-type and a lower surface thereof may be p-type.According to some exemplary embodiments, however, that the semiconductortypes of the upper surface and the lower surface of each of the LEDstacks may be reversed.

When the upper surface of the third LED stack 6300 is n-type, the uppersurface of the third LED stack 6300 may be surface textured throughchemical etching to form a roughened surface (or irregularities). Theupper surface of the first LED stack 6100 and the second LED stack 6200may also be roughened by surface texturing. Meanwhile, when the secondLED stack 6200 emits green light, since the green light has highervisibility than the red light or the blue light, it is preferable toincrease light emitting efficiency of the first LED stack 6100 and thethird LED stack 6300 as compared to that of the second LED stack 6200.Thus, surface texturing may be applied to the first LED stack 6100 andthe third LED stack 6300 to improve light extraction efficiency, and thesecond LED stack 6200 may be used without surface texturing to adjustthe intensity of red, green, and blue light to similar levels.

Light generated in the first LED stack 6100 may be transmitted throughthe second and third LED stacks 6200 and 6300 and emitted to theoutside. In addition, since the second LED stack 6200 emits light at alonger wavelength than the third LED stack 6300, light generated in thesecond LED stack 6200 may be transmitted through the third LED stack6300 and emitted to the outside.

The first color filter 6230 may be disposed between the first LED stack6100 and the second LED stack 6200. In addition, the second color filter6330 may be disposed between the second LED stack 6200 and the third LEDstack 6300. The first color filter 6230 transmits light generated in thefirst LED stack 6100 and reflects light generated in the second LEDstack 6200. The second color filter 6330 transmits light generated inthe first and second LED stacks 6100 and 6200 and reflects lightgenerated in the third LED stack 6300. Thus, light generated in thefirst LED stack 6100 may be emitted to the outside through the secondLED stack 6200 and the third LED stack 6300, and light generated in thesecond LED stack 6200 may be emitted to the outside through the thirdLED stack 6300. Further, it is possible to prevent light generated inthe second LED stack 6200 from being incident on the first LED stack6100 and lost, or light generated in the third LED stack 6300 from beingincident on the second LED stack 6200 and lost.

In some exemplary embodiments, the first color filter 6230 may reflectlight generated in the third LED stack 6300.

The first and second color filters 6230 and 6330 may be, for example, alow pass filter that passes through only a low frequency region, thatis, a long wavelength region, a band pass filter that passes throughonly a predetermined wavelength band, or a band stop filter that blocksonly the predetermined wavelength band. In particular, the first andsecond color filters 6200 and 6300 may be formed by alternately stackingthe insulating layers having different refractive indices. For example,the first and second color filters 6200 and 6300 may be formed byalternately stacking TiO₂ and SiO₂. In particular, the first and secondcolor filters 6200 and 6300 may include a distributed Bragg reflector(DBR). The stop band of the distributed Bragg reflector may becontrolled by adjusting a thickness of TiO₂ and SiO₂. The low passfilter and the band pass filter may also be formed by alternatelystacking the insulating layers having different refractive indices.

The first adhesive layer 6141 is disposed between the substrate 6021 andthe first LED stack 6100 and bonds the first LED stack 6100 to thesubstrate 6021. The second adhesive layer 6161 is disposed between thefirst LED stack 6100 and the second LED stack 6200 and bonds the secondLED stack 6200 to the first LED stack 6100. Further, the third adhesivelayer 6261 is disposed between the second LED stack 6200 and the thirdLED stack 6300 and bonds the third LED stack 6300 to the second LEDstack 6200.

As shown, the second adhesive layer 6161 may be disposed between thefirst LED stack 6100 and the first color filter 6230, and may contactthe first color filter 6230. The second adhesive layer 6161 transmitslight generated in the first LED stack 6100.

The third adhesive layer 6261 may be disposed between the second LEDstack 6200 and the second color filter 6330, and may contact the secondcolor filter 6330. The second adhesive layer 6161 transmits lightgenerated in the first LED stack 6100 and the second LED stack 6200.

Each of the first to third adhesive layers 6141, 6161, and 6261 isformed of an adhesive material that may be patterned. These adhesivelayers 6141, 6161, and 6261 may include, for example, epoxy, polyimide,SU8, spin-on glass (SOG), benzocyclobutene (BCB), or others, but are notlimited thereto.

A metal bonding material may be disposed in each of the adhesive layers6141, 6161, and 6261, which is described in more detail below.

The insulating layer 6130 is disposed between the first adhesive layer6141 and the first LED stack 6100. The insulating layer 6130 has amultilayer structure and may include a first insulating layer 6131 incontact with the first LED stack 6100 and a second insulating layer 6135in contact with the first adhesive layer 6141. The first insulatinglayer 6131 may be formed of a silicon nitride film (SiN_(x) layer), andthe second insulating layer 6135 may be formed of a silicon oxide film(SiO₂ layer). Since the silicon nitride film has strong adhesive forceto the GaP-based semiconductor layer and the SiO₂ layer has strongadhesive force to the first adhesive layer 6141, the first LED stack6100 may be stably fixed on the substrate 6021 by stacking the siliconnitride film and the SiO₂ layer.

According to an exemplary embodiment, a distributed Bragg reflector maybe further disposed between the first insulating layer 6131 and thesecond insulating layer 6135. The distributed Bragg reflector preventslight generated in the first LED stack 6100 from being absorbed into thesubstrate 6021, thereby improving light efficiency.

In FIG. 100A, while the first adhesive layer 6141 is shown and describedas being to divided into each pixel unit by the barrier 6350, the firstadhesive layer 6141 may be continuous over a plurality of pixels in someexemplary embodiments. The insulating layer 6130 may also be continuousover a plurality of pixels.

The first to third LED stacks 6100, 6200, and 6300 may be electricallyconnected to a circuit in the substrate 6021 using electrode pads,connectors, and ohmic electrodes, and thus, for example, a circuit asshown in FIG. 100B may be implemented. The electrode pads, connectors,and ohmic electrodes are described in more detail below.

FIG. 100B is a schematic circuit diagram of a display apparatusaccording to an exemplary embodiment.

Referring to FIG. 100B, a driving circuit according to an exemplaryembodiment may include two or more transistors Tr1 and Tr2 and acapacitor. When power supply is connected to selection lines Vrow1 toVrow3 and a data voltage is applied to the data lines Vdata1 to Vdata3,a voltage is applied to the corresponding light emitting diode. Further,charges are charged in the corresponding capacitor in accordance withthe values of Vdata1 to Vdata3. A turn-on state of the transistor Tr2may be maintained by the charged voltage of the capacitor, and thus evenwhen power is cut off to the selection line Vrow1, voltage of thecapacitor may be maintained and the voltage may be applied to the lightemitting diodes LED1 to LED3. Further, currents flowing through the LED1to the LED3 may be changed according to values of Vdata1 to Vdata3. Thecurrent may always be supplied through Vdd, and thus, continuous lightemission is possible.

The transistors Tr1 and Tr2 and the capacitor may be formed in thesubstrate 6021. Here, the light emitting diodes LED1 to LED3 maycorrespond to the first to third LED stacks 6100, 6200 and 6300 stackedin one pixel, respectively. Anodes of the first to third LED stacks6100, 6200 and 6300 are connected to the transistor Tr2, and cathodesthereof are grounded. The first to third LED stacks 6100, 6200, and 6300may be electrically grounded in common.

FIG. 100B exemplarily shows for a circuit diagram for an active matrixdriving, but other circuits for the active matrix driving may be used.In addition, according to an exemplary embodiment, passive matrixdriving may also be implemented.

Hereinafter, a manufacturing method of a display apparatus will bedescribed in detail.

FIGS. 101A to 107 are schematic plan views and cross-sectional viewsillustrating a method of manufacturing a display apparatus according toan exemplary embodiment. In each of the drawings, the cross-sectionalview is taken along line shown in the corresponding plan view.

First, referring to FIG. 101A, the first LED stack 6100 is grown on thefirst substrate 6121. The first substrate 6121 may be, for example, aGaAs substrate. The first LED stack 6100 is formed of AlGaInP-basedsemiconductor layers, and includes an n-type semiconductor layer 6123,an active layer, and a p-type semiconductor layer 6125. The first LEDstack 6100 may have, for example, a composition of Al, Ga, and In toemit red light.

The p-type semiconductor layer 6125 and the active layer are etched toexpose the n-type semiconductor layer 6123. The p-type semiconductorlayer 6125 and the active layer may be patterned using photolithographyand etching techniques. In FIG. 101A, although a portion correspondingto one pixel region is shown, the first LED stack 6100 may be formedover the plurality of pixel regions on the substrate 6121, and then-type semiconductor layer 6123 will be exposed corresponding to eachpixel region.

Referring to FIG. 101B, ohmic contact layers 6127 and 6129 are formed.The ohmic contact layers 6127 and 6129 may be formed for each pixelregion. The ohmic contact layer 6127 is in ohmic contact with the n-typesemiconductor layer 6123, and the ohmic contact layer 6129 is in ohmiccontact with the p-type semiconductor layer 6125. For example, the ohmiccontact layer 6127 may include AuTe or AuGe, and the ohmic contact layer6129 may include AuBe or AuZn.

Referring to FIG. 101C, an insulating layer 6130 is formed on the firstLED stack 6100. The insulating layer 6130 has a multilayer structure andis patterned to have openings that expose the ohmic contact layers 6127and 6129. The insulating layer 6130 may include a first insulating layer6131 and a second insulating layer 6135, and may also include adistributed Bragg reflector 6133. The second insulating layer 6135 maybe incorporated into the distributed Bragg reflector 6133 as a part ofthe distributed Bragg reflector 6133.

The first insulating layer 6131 may include, for example, a siliconnitride film, and the second insulating layer 6135 may include a siliconoxide film. The silicon nitride film exhibits good adhesion propertiesto the AlGaInP-based semiconductor layer, but the silicon oxide film haspoor adhesion properties to the AlGaInP-based semiconductor layer. Thesilicon oxide film has good adhesion to the first adhesive layer 6141,which will be described below, while the silicon nitride film has pooradhesion properties to the first adhesive layer 6141. Since the siliconnitride film and the silicon oxide film exhibit mutually complementarystress characteristics, it is possible to improve process stability byusing the silicon nitride film and the silicon oxide film together,thereby preventing occurrence of defects.

While the ohmic contact layers 6127 and 6129 are described as beingformed first, and the insulating layer 6130 is formed thereafter,according to some exemplary embodiments, the insulating layer 6130 maybe formed first, and the ohmic contact layers 6127 and 6129 may beformed in the openings of the insulating layer 6130 that expose then-type semiconductor layer 6123 and the p-type semiconductor layer 6125.

Referring to FIG. 101D, subsequently, first electrode pads 6137, 6138,6139, and 6140 are formed. The first electrode pads 6137 and 6139 areconnected to the ohmic contact layers 6127 and 6129 through the openingsof the insulating layer 6130, respectively. The first electrode pads6138 and 6140 are disposed on the insulating layer 6130 and areinsulated from the first LED stack 6100. As described below, the firstelectrode pads 6138 and 6140 will be electrically connected to thep-type semiconductor layers 6225 and 6325 of the second LED stack 6200and the third LED stack 6300, respectively. The first electrode pads6137, 6138, 6139, and 6140 may have a multilayer structure, andparticularly, may include a barrier metal layer on an upper surfacethereof.

Referring to FIG. 101E, a first adhesive layer 6141 is then formed onthe first electrode pads 6137, 6138, 6139, and 6140. The first adhesivelayer 6141 may contact the second insulating layer 6135.

The first adhesive layer 6141 is patterned to have openings that exposethe first electrode pads 6137, 6138, 6139, and 6140. As such, the firstadhesive layer 6141 is formed of a material that may be patterned, andmay be formed of, for example, epoxy, polyimide, SU8, SOG, BCB, orothers.

Metal bonding materials 6143 having substantially a ball shape areformed in the openings of the first adhesive layer 6141. The metalbonding material 6143 may be formed of, for example, an indium ball or asolder ball, such as AuSn, Sn, or the like. The metal bonding materials6143 having substantially a ball shape may have substantially the sameheight as a surface of the first adhesive layer 6141 or higher heightthan the surface of the first adhesive layer 6141. However, a volume ofeach metal bonding material may be smaller than a volume of the openingin the first adhesive layer 6141.

Referring to FIG. 102A, subsequently, the substrate 6021 and the firstLED stack 6100 are bonded. The electrode pads 6027, 6028, 6029 and 6030are disposed on the substrate 6021 in correspondence with the firstelectrode pads 6137, 6138, 6139 and 6140, and the metal bondingmaterials 6143 bond the first electrode pads 6137, 6138, 6139, and 6140with the electrode pads 6027, 6028, 6029, and 6030. Further, the firstadhesive layer 6141 bonds the substrate 6021 and the insulating layer6130.

The substrate 6021 may be a glass substrate on which a thin filmtransistor is formed, a Si substrate on which a CMOS transistor isformed, or others, for active matrix driving.

While the first electrode pads 6137 and 6139 are shown as being spacedapart from the ohmic contact layers 6127 and 6129, the first electrodepads 6137 and 6139 are electrically connected to the ohmic contactlayers 6127 and 6129 through the insulating layer 6130, respectively.

Although the first adhesive layer 6141 and the metal bonding materials6143 are described as being formed at the first substrate 6121 side, thefirst adhesive layer 6141 and the metal bonding materials 6143 may beformed at the substrate 6021 side, or adhesive layers may be formed atthe first substrate 6121 side and the substrate 6021 side, respectively,and these adhesive layers may be bonded to each other.

The metal bonding materials 6143 are pressed by these pads between thefirst electrode pads 6137, 6138, 6139, and 6140, and the electrode pads6027, 6028, 6029, and 6030 on the substrate 6021, and thus, upper andlower surfaces are deformed to have a flat shape according to the shapeof the electrode pads. Since the metal bonding materials 6143 aredeformed in the openings of the first adhesive layer 6141, the metalbonding materials 6143 may substantially completely fill the openings ofthe first adhesive layer 6141 to be in close contact with the firstadhesive layer 6141, or an empty space may be formed in the openings ofthe first adhesive layer 6141. The first adhesive layer 6141 maycontract in a vertical direction and may expand in a horizontaldirection under heating and pressurizing condition, and thus a shape ofan inner wall of the openings may be deformed.

The shapes of the metal bonding members 6143 and the first adhesivelayer 6141 are described below with reference to FIGS. 108A, 108B, and108C.

Referring to FIG. 102B, the first substrate 6121 is removed, and then-type semiconductor layer 6123 is exposed. The first substrate 6121 maybe removed using a wet etching technique or the like. A surfaceroughened by surface texturing may be formed on the surface of theexposed n-type semiconductor layer 6123.

Referring to FIG. 102C, holes H1 passing through the first LED stack6100 and the insulating layer 6130 may be formed using a hard mask orthe like. The holes H1 may expose the first electrode pads 6137, 6138,and 6140, respectively. The hole H1 is not formed on the first electrodepad 6139, and thus the first electrode pad 6139 is not exposed throughthe first LED stack 6100.

Then, an insulating layer 6153 is formed to cover the surface of thefirst LED stack 6100 and side walls of the holes H1. The insulatinglayer 6153 is patterned to expose the first electrode pads 6137, 6138,6139, and 6140 in the holes H1. The insulating layer 6153 may include asilicon nitride film or a silicon oxide film.

Referring to FIG. 102D, first connectors 6157, 6158, and 6160 that areelectrically connected to the first electrode pads 6137, 6138, and 6140through the holes H1, respectively, are formed.

The first-1 connector 6157 is connected to the first electrode pad 6137,the first-2 connector 6158 is connected to the first electrode pad 6138,and the first-3 connector 6160 is connected to the first electrode pad6140. The first electrode pad 6140 is electrically connected to then-type semiconductor layer 6123 of the first LED stack 6100, and thusthe first connector 6157 is also electrically connected to the n-typesemiconductor layer 6123. The first-2 connector 6158 and the first-3connector 6160 are electrically insulated from the first LED stack 6100.

Referring to FIG. 102E, a second adhesive layer 6161 is then formed onthe first connectors 6157, 6158, and 6160. The second adhesive layer6161 may contact the insulating layer 6153.

The second adhesive layer 6161 is patterned to have openings that exposethe first connectors 6157, 6158, and 6160. As such, the second adhesivelayer 6161 is formed of a material that may be patterned similarly tothe first adhesive layer 6141, and may be formed of, for example, epoxy,polyimide, SU8, SOG, BCB, or others.

Metal bonding materials 6163 having substantially a ball shape areformed in the openings of the second adhesive layer 6161. The materialand shape of the metal bonding material 6163 are similar to those of themetal bonding material 6143 described above, and thus, detaileddescriptions thereof are omitted.

Referring to FIG. 103A, the second LED stack 6200 is grown on a secondsubstrate 6221, and a second transparent electrode 6229 is formed on thesecond LED stack 6200.

The second substrate 6221 may be a substrate capable of growing thesecond LED stack 6200, for example, a sapphire substrate or a GaAssubstrate.

The second LED stack 6200 may be formed of AlGaInP-based semiconductorlayers or AlGaInN-based semiconductor layers. The second LED stack 6200may include an n-type semiconductor layer 6223, a p-type semiconductorlayer 6225, and an active layer, and the active layer may have amultiple quantum well structure. A composition ratio of the well layerin the active layer may be determined so that the second LED stack 6200emits green light, for example.

The second transparent electrode 6229 is in ohmic contact with thep-type semiconductor layer. The second transparent electrode 6229 may beformed of a metal layer or a conductive oxide layer which is transparentto red light and green light. Examples of the conductive oxide layer mayinclude SnO₂, InO₂, ITO, ZnO, IZO, or others.

Referring to FIG. 103B, the second transparent electrode 6229, thep-type semiconductor layer 6225, and the active layer are patterned topartially expose the n-type semiconductor layer 6223. The n-typesemiconductor layer 6223 will be exposed in a plurality of regionscorresponding to a plurality of pixel regions on the second substrate6221.

Although the n-type semiconductor layer 6223 is described as beingexposed after the second transparent electrode 6229 is formed, in someexemplary embodiments, the n-type semiconductor layer 6223 may beexposed first and the second transparent electrode 6229 may be formedthereafter.

Referring to FIG. 103C, a first color filter 6230 is formed on thesecond transparent electrode 6229. The first color filter 6230 is formedto transmit light generated in the first LED stack 6100 and to reflectlight generated in the second LED stack 6200.

Then, an insulating layer 6231 may be formed on the first color filter6230. The insulating layer 6231 may be formed to control stress and maybe formed of, for example, a silicon nitride film (SiN_(x)) or a siliconoxide film (SiO₂). The insulating layer 6231 may be formed first beforethe first color filter 6230 is formed.

Openings exposing the n-type semiconductor layer 6223 and the secondtransparent electrode 6229 are formed by patterning the insulating layer6231 and the first color filter 6230.

Although the first color filter 6230 is described as being formed afterthe n-type semiconductor layer 6223 is exposed, according to someexemplary embodiments, the first color filter 6230 may be formed first,and then, the first color filter 6230, the second transparent electrode6229, the p-type semiconductor layer 6225, and the active layer may bepatterned to expose the n-type semiconductor layer 6223. Then, theinsulating layer 6231 may be formed to cover side surfaces of the p-typesemiconductor layer 6225 and the active layer.

Referring to FIG. 103D, subsequently, the second electrode pads 6237,6238, and 6240 are formed on the first color filter 6230 or theinsulating layer 6231. The second electrode pad 6237 may be electricallyconnected to the n-type semiconductor layer 6223 through the opening ofthe first color filter 6230, and the second electrode pad 6238 may beelectrically connected to the second transparent electrode 6229 throughthe opening of the first color filter 6230. The second electrode pad6240 is disposed on the first color filter 6240 and is insulated fromthe second LED stack 6200.

Referring to FIG. 104A, the second LED stack 6200 and the secondelectrode pads 6237, 6238, and 6240 that are described with reference toFIG. 103D, are coupled on the second adhesive layer 6161 and the metalbonding materials 6163 that are described with reference to FIG. 102E.The metal bonding materials 6163 may bond the first connectors 6157,6158, and 6160 and the second electrode pads 6237, 6238, and 6240,respectively, and the second adhesive layer 6161 may bond the insulatinglayer 6231 and the insulating layer 6153. The bonding using the secondadhesive layer 6161 and the metal bonding materials 6163 is similar tothat described with reference to FIG. 102A, and thus, detaileddescription thereof are omitted.

The second substrate 6221 is separated from the second LED stack 6200,and the surface of the second LED stack 6200 is exposed. The secondsubstrate 6221 may be separated using a technique such as etching, laserlift-off, or the like. A surface roughened by surface texturing may beformed on the surface of the exposed second LED stack 6200, that is, thesurface of the n-type semiconductor layer 6223.

Although the second adhesive layer 6161 and the metal bonding materials6163 are described as being formed on the first LED stack 6100 to bondthe second LED stack 6200, according to some exemplary embodiments, thesecond adhesive layer 6161 and the metal bonding materials 6163 may beformed at the second LED stack 6200 side. Further, an adhesive layer maybe formed on the first LED stack 6100 and the second LED stack 6200,respectively, and these adhesive layers may be bonded to each other.

Referring to FIG. 104B, holes H2 passing through the second LED stack6200, the second transparent electrode 6229, the first color filter6230, and the insulating layer 6231 may be formed using a hard mask orthe like. The holes H2 may expose the second electrode pads 6237 and6240, respectively. The hole H2 is not formed on the second electrodepad 238, and thus, the second electrode pad 238 is not exposed throughthe second LED stack 6200.

Then, an insulating layer 6253 is formed to cover the surface of thesecond LED stack 6200 and side walls of the holes H2. The insulatinglayer 6253 is patterned to expose the second electrode pads 6237 and6240 in the holes H2. The insulating layer 6253 may include a siliconnitride film or a silicon oxide film.

Referring to FIG. 104C, second connectors 6257 and 6260 that areelectrically connected to the second electrode pads 6237 and 6240through the holes H2, respectively, are formed. The second-1 connector6257 is connected to the second electrode pad 6237 and thus electricallyconnected to the n-type semiconductor layer 6223. The second-2 connector6260 is insulated from the second LED stack 6200 and insulated from thefirst LED stack 6100.

Further, the second-1 connector 6257 is electrically connected to theelectrode pad 6027 through the first-1 connector 6157, and the second-2connector 6260 is electrically connected to the electrode pad 6030through the first-3 connector 6160. The second-1 connector 6257 may bestacked in a vertical direction to the first-1 connector 6157, and thesecond-2 connector 6260 may be stacked in a vertical direction to thefirst-3 connector 6160. However, the inventive concepts are not limitedthereto.

Referring to FIG. 104D, a third adhesive layer 6261 is then formed onthe second connectors 6257 and 6260. The third adhesive layer 6261 maycontact the insulating layer 6253.

The third adhesive layer 6261 is patterned to have openings that exposethe second connectors 6257 and 6260. As such, the third adhesive layer6261 is formed of a material that may be patterned similarly to thefirst adhesive layer 6141, and may be formed of, for example, epoxy,polyimide, SU8, SOG, BCB, or others.

Metal bonding materials 6263 having substantially a ball shape areformed in the openings of the third adhesive layer 6261. The materialand shape of the metal bonding material 6263 are similar to those of themetal bonding material 6143 described above, and thus, detaileddescriptions thereof are omitted.

Referring to FIG. 105A, the third LED stack 6300 is grown on a thirdsubstrate 6321, and a third transparent electrode 6329 is formed on thethird LED stack 6300.

The third substrate 6321 may be a substrate capable of growing the thirdLED stack 6300, for example, a sapphire substrate. The third LED stack6300 may be formed of AlGaInN-based semiconductor layers. The third LEDstack 6300 may include an n-type semiconductor layer 6323, a p-typesemiconductor layer 6325, and an active layer, and the active layer mayhave a multiple quantum well structure. A composition ratio of the welllayer in the active layer may be determined so that the third LED stack6300 emits blue light, for example.

The third transparent electrode 6329 is in ohmic contact with the p-typesemiconductor layer 6325. The third transparent electrode 6329 may beformed of a metal layer or a conductive oxide layer which is transparentto red light, green light, and blue light. Examples of the conductiveoxide layer may include SnO₂, InO₂, ITO, ZnO, IZO, or others.

Referring to FIG. 105B, the third transparent electrode 6329, the p-typesemiconductor layer 6325, and the active layer are patterned topartially expose the n-type semiconductor layer 6323. The n-typesemiconductor layer 6323 will be exposed in a plurality of regionscorresponding to a plurality of pixel regions on the third substrate6321.

Although the n-type semiconductor layer 6323 is described as beingexposed after the third transparent electrode 6329 is formed, accordingto some exemplary embodiments, the n-type semiconductor layer 6323 maybe exposed before the first and the third transparent electrode 6329 maybe formed.

Referring to FIG. 105C, a second color filter 6330 is formed on thethird transparent electrode 6329. The second color filter 6330 is formedto transmit light generated in the first LED stack 6100 and the secondLED stack 6200, and to reflect light generated in the third LED stack6300.

Then, an insulating layer 6331 may be formed on the second color filter6330. The insulating layer 6331 may be formed to control stress and maybe formed of, for example, a silicon nitride film (SiN_(x)) or a siliconoxide film (SiO₂). The insulating layer 6331 may be formed first beforethe second color filter 6330 is formed. Meanwhile, openings exposing then-type semiconductor layer 6323 and the second transparent electrode6329 are formed by patterning the insulating layer 6331 and the secondcolor filter 6330.

Although the second color filter 6330 is described as being formed afterthe n-type semiconductor layer 6323 is exposed, according to someexemplary embodiments, the second color filter 6330 may be formed first,and the second color filter 6330, the third transparent electrode 6329,the p-type semiconductor layer 6325, and the active layer may bepatterned to expose the n-type semiconductor layer 6323 thereafter.Then, the insulating layer 6331 may be formed to cover side surfaces ofthe p-type semiconductor layer 6325 and the active layer.

Referring to FIG. 105D, subsequently, the third electrode pads 6337 and6340 are formed on the second color filter 6330 or the insulating layer6331. The third electrode pad 6337 may be electrically connected to then-type semiconductor layer 6323 through the opening of the second colorfilter 6330, and the third electrode pad 6340 may be electricallyconnected to the third transparent electrode 6329 through the opening ofthe second color filter 6330.

Referring to FIG. 106A, the third LED stack 6300 and the third electrodepads 6337 and 6340 that are described with reference to FIG. 105D, arecoupled to the third adhesive layer 6261 by the metal bonding materials6263 that are described with reference to FIG. 104E. The metal bondingmaterials 6263 may bond the second connectors 6257 and 6260 and thethird electrode pads 6337 and 6340, respectively, and the third adhesivelayer 6261 may bond the insulating layer 6331 and the insulating layer6253. The bonding using the third adhesive layer 6261 and the metalbonding materials 6263 is similar to that described with reference toFIG. 102A, and thus, detailed descriptions thereof are omitted.

The third substrate 6321 is separated from the third LED stack 6300, andthe surface of the third LED stack 6300 is exposed. The third substrate6321 may be separated using a technique such as laser lift-off, chemicallift-off, or others. A surface roughened by surface texturing may beformed on the surface of the exposed third LED stack 6300, that is, thesurface of the n-type semiconductor layer 6323.

Although the third adhesive layer 6261 and the metal bonding materials6263 are described as being formed on the second LED stack 6200 to bondthe third LED stack 6300, according to some exemplary embodiments, thethird adhesive layer 6261 and the metal bonding materials 6263 may beformed at the third LED stack 6300 side. Further, an adhesive layer maybe formed on the second LED stack 6200 and the third LED stack 6300,respectively, and these adhesive layers may be bonded to each other.

Referring to FIG. 106B, subsequently, regions between adjacent pixelsare then etched to separate the pixels, and an insulating layer 6341 maybe formed. The insulating layer 6341 may cover a side surface and anupper surface of each pixel. A region between adjacent pixels may beremoved to expose the substrate 6021, but the inventive concepts are notlimited thereto. For example, the first adhesive layer 6141 may beformed continuously over a plurality of pixel regions without beingseparated, and the insulating layer 6130 may also be continuous.

Referring to FIG. 107, subsequently, a barrier 6350 may be formed in aseparation region between the pixel regions. The barrier 6350 may beformed of a light reflecting layer or a light absorbing layer, and thuslight interference between pixels may be prevented. The light reflectinglayer may include, for example, a white PSR, a distributed Braggreflector, an insulating layer such as SiO₂, and a reflective metallayer deposited thereon, or a highly reflective organic layer. For alight blocking layer, black epoxy, for example, may be used.

Thus, a display apparatus according to an exemplary embodiment, in whicha plurality of pixels are arranged on the substrate 6021, may beprovided. The first to third LED stacks 6100, 6200, and 6300 in eachpixel may be independently driven by power input through the electrodepads 6027, 6028, 6029, and 6030.

FIGS. 108A, 108B, and 108C are schematic cross-sectional views of themetal bonding materials 6143, 6163, and 6263.

Referring to FIG. 108A, the metal bonding materials 6143, 6163, and 6263are disposed in the openings in the first to third adhesive layers 6141,6161, and 6261. A lower surface of the metal bonding materials 6143,6163, and 6263 is in contact with the electrode pads 6030 or theconnector 6160 or 6260, and thus, the metal bonding materials 6143,6163, and 6263 may have substantially a flat shape depending on an uppersurface shape of the electrode pads or connectors. The upper surfaces ofthe metal bonding materials 6143, 6163, and 6263 may have substantiallya flat shape depending on the shape of the electrode pads 6140, 6240,and 6340. A side surface of the metal bonding materials 6143, 6163, and6263 may have a substantially curved shape. A central portion of themetal bonding materials 6143, 6163, and 6263 may have a convex shape tothe outside.

An inner wall of the openings of the adhesive layers 6141, 6161, and6261 may also have substantially a convex shape inward of the openings,and side surfaces of the metal bonding materials 6143, 6163 and 6263 maybe in contact with side surfaces of the adhesive layers 6141, 6161 and6261. However, if volume of the metal bonding materials 6143, 6163, and6263 is less than volume of the openings of the adhesive layers 6141,6161, and 6261, an empty space may be formed in the openings as shown.

Referring to FIG. 108B, the shapes of the metal bonding materials 6143,6163, and 6263 and the adhesive layers 6141, 6161, and 6261 according toan exemplary embodiment are substantially similar to those describedwith reference to FIG. 108A, but there is a difference in that a convexportion of the side surface is disposed at a relatively lower positionby heating.

Referring to FIG. 108C, the shapes of the metal bonding materials 6143,6163, and 6263 according to an exemplary embodiment are similar to thosedescribed with reference to FIG. 108B, but are different from shapes ofinner walls of the openings of the adhesive layers 6141, 6161, and 6261.In particular, the inner wall of the opening may be formed to be concaveby the metal bonding material.

Although certain exemplary embodiments and implementations have beendescribed herein, other embodiments and modifications will be apparentfrom this description. Accordingly, the inventive concepts are notlimited to such embodiments, but rather to the broader scope of theappended claims and various obvious modifications and equivalentarrangements as would be apparent to a person of ordinary skill in theart.

What is claimed is:
 1. A light emitting device for a display,comprising: a first LED sub-unit; a second LED sub-unit disposed belowthe first LED sub-unit; a third LED sub-unit disposed below the secondLED sub-unit; an insulating layer substantially covering the first,second, and third LED sub-units; and electrode pads electricallyconnected to the first, second, and third LED sub-units, the electrodepads comprising a common electrode pad, a first electrode pad, a secondelectrode pad, and a third electrode pad, wherein: the first LEDsub-unit is disposed on a partial region of the second LED sub-unit; thesecond LED sub-unit is disposed on a partial region of the third LEDsub-unit; the insulating layer has openings for electrical connectionbetween the electrode pads; the common electrode pad is connected to thefirst, second, and third LED sub-units through the openings in theinsulating layer; is the first, second, and third electrode pads areconnected to the first, second, and third LED sub-units, respectively,through at least one of the openings; and the first, second, and thirdLED sub-units are configured to be independently driven using theelectrode pads.
 2. The light emitting device of claim 1, wherein: lightgenerated in the first LED sub-unit is configured to be emitted to theoutside of the light emitting device through the second LED sub-unit andthe third LED sub-unit; and light generated in the second LED sub-unitis configured to be emitted to the outside of the light emitting devicethrough the third LED sub-unit.
 3. The light emitting device of claim 2,wherein the first, second, and third LED sub-units comprise first,second, and third LED stacks configured to emit red light, green light,and blue light, respectively.
 4. The light emitting device of claim 2,wherein the light emitting device comprises a micro light emitting diodehaving a surface area less than about 10,000 square μm.
 5. The lightemitting device of claim 4, wherein: the first LED sub-unit isconfigured to emit any one of red, green, and blue light; the second LEDsub-unit is configured to emit a different one of red, green, and bluelight from the first LED sub-unit; and a third LED sub-unit isconfigured to emit a different one of red, green, and blue light fromthe first and second LED sub-units.
 6. The light emitting device ofclaim 1, further comprising: a first transparent electrode interposedbetween the first LED sub-unit and the second LED sub-unit and in ohmiccontact with a lower surface of the first LED sub-unit; a secondtransparent electrode interposed between the second LED sub-unit and thethird LED sub-unit and in ohmic contact with a lower surface of thesecond LED sub-unit; and a third transparent electrode disposed to be inohmic contact with an upper surface of the third LED sub-unit, whereinat least some of the openings in the insulating layer expose the first,second, and third transparent electrodes.
 7. The light emitting deviceof claim 6, wherein one of the openings in the insulating layer exposesthe second transparent electrode and the third transparent electrodetogether.
 8. The light emitting device of claim 7, wherein: the first,second, and third LED sub-units each comprises a first conductivity typesemiconductor layer and a second conductivity type semiconductor layer;the first, second, and third transparent electrodes are electricallyconnected to the second conductivity type semiconductor layers of thefirst, second, and third LED sub-units, respectively; and the secondconductivity type semiconductor layer of the third LED sub-unit isdisposed on a partial region of the first conductivity typesemiconductor layer of the third LED sub-unit.
 9. The light emittingdevice of claim 8, wherein the first LED sub-unit and the second LEDsub-unit are disposed in an upper region of the second conductivity typesemiconductor layer of the third LED sub-unit.
 10. The light emittingdevice of claim 8, wherein the second and third electrode pads areelectrically connected to the first conductivity type semiconductorlayer of the second LED sub-unit and the first conductivity typesemiconductor layer of the third LED sub-unit, respectively.
 11. Thelight emitting device of claim 9, wherein the second and third electrodepads are directly connected to the first conductivity type semiconductorlayers of the second LED sub-unit and the third LED sub-unit,respectively.
 12. The light emitting device of claim 6, furthercomprising: a first color filter disposed between the third transparentelectrode and the second transparent electrode; and a second colorfilter having a different refractive index than the first color filter,and disposed between the second LED sub-unit and the first transparentelectrode.
 13. The light emitting device of claim 12, furthercomprising: a first bonding layer interposed between the first colorfilter and the second transparent electrode; and a second bonding layerinterposed between the second color filter and the first transparentelectrode.
 14. The light emitting device of claim 1, further comprising:a substrate connected to a lower surface of the third LED sub-unit,wherein the substrate comprises at least one of a sapphire material anda gallium nitride material.
 15. The light emitting device of claim 1,wherein the second LED sub-unit and the third LED sub-unit are connectedin common through one of the openings in the insulating layer.
 16. Thelight emitting device of claim 1, further comprising an ohmic electrodedisposed between the electrode pads and the first LED sub-unit and inohmic contact with the first LED sub-unit, wherein: the first electrodepad is connected to the ohmic electrode; and the insulating layercomprises at least one of a light reflecting layer and a light absorbinglayer.
 17. A display apparatus comprising: a circuit board having adriving circuit to drive the light emitting devices in an active matrixdriving mode or passive matrix driving mode; and a plurality of lightemitting devices flip-bonded on the circuit board, at least some of thelight emitting devices comprise the light emitting device of claim 1,wherein the electrode pads are electrically connected to the circuitboard.
 18. The display apparatus of claim 17, wherein: the lightemitting devices comprise respective substrates adjoined to the thirdLED sub-unit; and the substrates are spaced apart from each other.
 19. Alight emitting stacked structure, comprising: a substrate including anupper surface and a lower surface; a plurality of sequentially stackedepitaxial sub-units disposed on the substrate and configured to emitlight of different wavelength bands, each epitaxial sub-unit has a lightemitting region that overlaps with the light emitting region of anadjacent epitaxial sub unit; and a substantially, non-transmissive filmcovering at least a portion of side surfaces of the epitaxial sub-units,wherein the side surfaces of the epitaxial sub-units are inclined withrespect to one of the upper and lower surfaces of the substrate.
 20. Alight-emitting diode (LED) pixel for a display, comprising: a first LEDsub-unit; a second LED sub-unit disposed on the first LED sub-unit; athird LED sub-unit disposed on the second LED sub-unit; a connectordisposed on at least one side surface of the first, second, and thirdLED sub-units and electrically connected to at least one of the LEDsub-units; and an insulating layer to insulate the connector from the atleast one side surface of the LED sub-units, wherein: the at least oneside surface of the LED sub-units is inclined with respect to a bottomsurface of one of the first, second, and third LED sub-units; and theconnector is disposed on the inclined side surface of the LED sub-units.